Amiga Magazin: Amiga-CD 1996 July/AMIGA_1996_7.BIN/ausgabe_7_96/pd-programmierung/perl5_002bin.lha/man/catp/perlsyn.0

Text File | 1996-03-02 | 43KB | 727 lines

PERLSYN(1)     User Contributed Perl Documentation     PERLSYN(1)


NNNNAAAAMMMMEEEE
       perlsyn - Perl syntax

DDDDEEEESSSSCCCCRRRRIIIIPPPPTTTTIIIIOOOONNNN
       A Perl script consists of a sequence of declarations and
       statements.  The only things that need to be declared in
       Perl are report formats and subroutines.  See the sections
       below for more information on those declarations.  All
       uninitialized user-created objects are assumed to start
       with a null or 0 value until they are defined by some
       explicit operation such as assignment.  (Though you can
       get warnings about the use of undefined values if you
       like.)  The sequence of statements is executed just once,
       unlike in sssseeeedddd and aaaawwwwkkkk scripts, where the sequence of
       statements is executed for each input line.  While this
       means that you must explicitly loop over the lines of your
       input file (or files), it also means you have much more
       control over which files and which lines you look at.
       (Actually, I'm lying--it is possible to do an implicit
       loop with either the ----nnnn or ----pppp switch.  It's just not the
       mandatory default like it is in sssseeeedddd and aaaawwwwkkkk.)

       DDDDeeeeccccllllaaaarrrraaaattttiiiioooonnnnssss

       Perl is, for the most part, a free-form language.  (The
       only exception to this is format declarations, for obvious
       reasons.) Comments are indicated by the "#" character, and
       extend to the end of the line.  If you attempt to use ////****
       ****//// C-style comments, it will be interpreted either as
       division or pattern matching, depending on the context,
       and C++ //////// comments just look like a null regular
       expression, so don't do that.

       A declaration can be put anywhere a statement can, but has
       no effect on the execution of the primary sequence of
       statements--declarations all take effect at compile time.
       Typically all the declarations are put at the beginning or
       the end of the script.  However, if you're using
       lexically-scoped private variables created with _m_y_(_),
       you'll have to make sure your format or subroutine
       definition is within the same block scope as the my if you
       expect to to be able to access those private variables.

       Declaring a subroutine allows a subroutine name to be used
       as if it were a list operator from that point forward in
       the program.  You can declare a subroutine (prototyped to
       take one scalar parameter) without defining it by saying
       just:

           ssssuuuubbbb mmmmyyyynnnnaaaammmmeeee (((($$$$))));;;;
           $$$$mmmmeeee ==== mmmmyyyynnnnaaaammmmeeee $$$$0000             oooorrrr ddddiiiieeee """"ccccaaaannnn''''tttt ggggeeeetttt mmmmyyyynnnnaaaammmmeeee"""";;;;

       Note that it functions as a list operator though, not as a
       unary operator, so be careful to use oooorrrr instead of ||||||||



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       there.

       Subroutines declarations can also be loaded up with the
       rrrreeeeqqqquuuuiiiirrrreeee statement or both loaded and imported into your
       namespace with a uuuusssseeee statement.  See the _p_e_r_l_m_o_d manpage
       for details on this.

       A statement sequence may contain declarations of
       lexically-scoped variables, but apart from declaring a
       variable name, the declaration acts like an ordinary
       statement, and is elaborated within the sequence of
       statements as if it were an ordinary statement.  That
       means it actually has both compile-time and run-time
       effects.

       SSSSiiiimmmmpppplllleeee ssssttttaaaatttteeeemmmmeeeennnnttttssss

       The only kind of simple statement is an expression
       evaluated for its side effects.  Every simple statement
       must be terminated with a semicolon, unless it is the
       final statement in a block, in which case the semicolon is
       optional.  (A semicolon is still encouraged there if the
       block takes up more than one line, since you may
       eventually add another line.)  Note that there are some
       operators like eeeevvvvaaaallll {{{{}}}} and ddddoooo {{{{}}}} that look like compound
       statements, but aren't (they're just TERMs in an
       expression), and thus need an explicit termination if used
       as the last item in a statement.

       Any simple statement may optionally be followed by a
       _S_I_N_G_L_E modifier, just before the terminating semicolon (or
       block ending).  The possible modifiers are:

           iiiiffff EEEEXXXXPPPPRRRR
           uuuunnnnlllleeeessssssss EEEEXXXXPPPPRRRR
           wwwwhhhhiiiilllleeee EEEEXXXXPPPPRRRR
           uuuunnnnttttiiiillll EEEEXXXXPPPPRRRR

       The iiiiffff and uuuunnnnlllleeeessssssss modifiers have the expected semantics,
       presuming you're a speaker of English.  The wwwwhhhhiiiilllleeee and
       uuuunnnnttttiiiillll modifiers also have the usual "while loop" semantics
       (conditional evaluated first), except when applied to a
       do-BLOCK (or to the now-deprecated do-SUBROUTINE
       statement), in which case the block executes once before
       the conditional is evaluated.  This is so that you can
       write loops like:

           ddddoooo {{{{
               $$$$lllliiiinnnneeee ==== <<<<SSSSTTTTDDDDIIIINNNN>>>>;;;;
               ............
           }}}} uuuunnnnttttiiiillll $$$$lllliiiinnnneeee  eeeeqqqq """"....\\\\nnnn"""";;;;

       See the ddddoooo entry in the _p_e_r_l_f_u_n_c manpage.  Note also that
       the loop control statements described later will _N_O_T work



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       in this construct, since modifiers don't take loop labels.
       Sorry.  You can always wrap another block around it to do
       that sort of thing.

       CCCCoooommmmppppoooouuuunnnndddd ssssttttaaaatttteeeemmmmeeeennnnttttssss

       In Perl, a sequence of statements that defines a scope is
       called a block.  Sometimes a block is delimited by the
       file containing it (in the case of a required file, or the
       program as a whole), and sometimes a block is delimited by
       the extent of a string (in the case of an eval).

       But generally, a block is delimited by curly brackets,
       also known as braces.  We will call this syntactic
       construct a BLOCK.

       The following compound statements may be used to control
       flow:

           iiiiffff ((((EEEEXXXXPPPPRRRR)))) BBBBLLLLOOOOCCCCKKKK
           iiiiffff ((((EEEEXXXXPPPPRRRR)))) BBBBLLLLOOOOCCCCKKKK eeeellllsssseeee BBBBLLLLOOOOCCCCKKKK
           iiiiffff ((((EEEEXXXXPPPPRRRR)))) BBBBLLLLOOOOCCCCKKKK eeeellllssssiiiiffff ((((EEEEXXXXPPPPRRRR)))) BBBBLLLLOOOOCCCCKKKK ............ eeeellllsssseeee BBBBLLLLOOOOCCCCKKKK
           LLLLAAAABBBBEEEELLLL wwwwhhhhiiiilllleeee ((((EEEEXXXXPPPPRRRR)))) BBBBLLLLOOOOCCCCKKKK
           LLLLAAAABBBBEEEELLLL wwwwhhhhiiiilllleeee ((((EEEEXXXXPPPPRRRR)))) BBBBLLLLOOOOCCCCKKKK ccccoooonnnnttttiiiinnnnuuuueeee BBBBLLLLOOOOCCCCKKKK
           LLLLAAAABBBBEEEELLLL ffffoooorrrr ((((EEEEXXXXPPPPRRRR;;;; EEEEXXXXPPPPRRRR;;;; EEEEXXXXPPPPRRRR)))) BBBBLLLLOOOOCCCCKKKK
           LLLLAAAABBBBEEEELLLL ffffoooorrrreeeeaaaacccchhhh VVVVAAAARRRR ((((LLLLIIIISSSSTTTT)))) BBBBLLLLOOOOCCCCKKKK
           LLLLAAAABBBBEEEELLLL BBBBLLLLOOOOCCCCKKKK ccccoooonnnnttttiiiinnnnuuuueeee BBBBLLLLOOOOCCCCKKKK

       Note that, unlike C and Pascal, these are defined in terms
       of BLOCKs, not statements.  This means that the curly
       brackets are _r_e_q_u_i_r_e_d--no dangling statements allowed.  If
       you want to write conditionals without curly brackets
       there are several other ways to do it.  The following all
       do the same thing:

           iiiiffff ((((!!!!ooooppppeeeennnn((((FFFFOOOOOOOO)))))))) {{{{ ddddiiiieeee """"CCCCaaaannnn''''tttt ooooppppeeeennnn $$$$FFFFOOOOOOOO:::: $$$$!!!!"""";;;; }}}}
           ddddiiiieeee """"CCCCaaaannnn''''tttt ooooppppeeeennnn $$$$FFFFOOOOOOOO:::: $$$$!!!!"""" uuuunnnnlllleeeessssssss ooooppppeeeennnn((((FFFFOOOOOOOO))));;;;
           ooooppppeeeennnn((((FFFFOOOOOOOO)))) oooorrrr ddddiiiieeee """"CCCCaaaannnn''''tttt ooooppppeeeennnn $$$$FFFFOOOOOOOO:::: $$$$!!!!"""";;;;     #### FFFFOOOOOOOO oooorrrr bbbbuuuusssstttt!!!!
           ooooppppeeeennnn((((FFFFOOOOOOOO)))) ???? ''''hhhhiiii mmmmoooommmm'''' :::: ddddiiiieeee """"CCCCaaaannnn''''tttt ooooppppeeeennnn $$$$FFFFOOOOOOOO:::: $$$$!!!!"""";;;;
                               #### aaaa bbbbiiiitttt eeeexxxxoooottttiiiicccc,,,, tttthhhhaaaatttt llllaaaasssstttt oooonnnneeee

       The iiiiffff statement is straightforward.  Since BLOCKs are
       always bounded by curly brackets, there is never any
       ambiguity about which iiiiffff an eeeellllsssseeee goes with.  If you use
       uuuunnnnlllleeeessssssss in place of iiiiffff, the sense of the test is reversed.

       The wwwwhhhhiiiilllleeee statement executes the block as long as the
       expression is true (does not evaluate to the null string
       or 0 or "0").  The LABEL is optional, and if present,
       consists of an identifier followed by a colon.  The LABEL
       identifies the loop for the loop control statements nnnneeeexxxxtttt,
       llllaaaasssstttt, and rrrreeeeddddoooo.  If the LABEL is omitted, the loop control
       statement refers to the innermost enclosing loop.  This
       may include dynamically looking back your call-stack at



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       run time to find the LABEL.  Such desperate behavior
       triggers a warning if you use the ----wwww flag.

       If there is a ccccoooonnnnttttiiiinnnnuuuueeee BLOCK, it is always executed just
       before the conditional is about to be evaluated again,
       just like the third part of a ffffoooorrrr loop in C.  Thus it can
       be used to increment a loop variable, even when the loop
       has been continued via the nnnneeeexxxxtttt statement (which is
       similar to the C ccccoooonnnnttttiiiinnnnuuuueeee statement).

       LLLLoooooooopppp CCCCoooonnnnttttrrrroooollll

       The nnnneeeexxxxtttt command is like the ccccoooonnnnttttiiiinnnnuuuueeee statement in C; it
       starts the next iteration of the loop:

           LLLLIIIINNNNEEEE:::: wwwwhhhhiiiilllleeee ((((<<<<SSSSTTTTDDDDIIIINNNN>>>>)))) {{{{
               nnnneeeexxxxtttt LLLLIIIINNNNEEEE iiiiffff ////^^^^####////;;;;      #### ddddiiiissssccccaaaarrrrdddd ccccoooommmmmmmmeeeennnnttttssss
               ............
           }}}}

       The llllaaaasssstttt command is like the bbbbrrrreeeeaaaakkkk statement in C (as used
       in loops); it immediately exits the loop in question.  The
       ccccoooonnnnttttiiiinnnnuuuueeee block, if any, is not executed:

           LLLLIIIINNNNEEEE:::: wwwwhhhhiiiilllleeee ((((<<<<SSSSTTTTDDDDIIIINNNN>>>>)))) {{{{
               llllaaaasssstttt LLLLIIIINNNNEEEE iiiiffff ////^^^^$$$$////;;;;      #### eeeexxxxiiiitttt wwwwhhhheeeennnn ddddoooonnnneeee wwwwiiiitttthhhh hhhheeeeaaaaddddeeeerrrr
               ............
           }}}}

       The rrrreeeeddddoooo command restarts the loop block without
       evaluating the conditional again.  The ccccoooonnnnttttiiiinnnnuuuueeee block, if
       any, is _n_o_t executed.  This command is normally used by
       programs that want to lie to themselves about what was
       just input.

       For example, when processing a file like _/_e_t_c_/_t_e_r_m_c_a_p.  If
       your input lines might end in backslashes to indicate
       continuation, you want to skip ahead and get the next
       record.

           wwwwhhhhiiiilllleeee ((((<<<<>>>>)))) {{{{
               cccchhhhoooommmmpppp;;;;
               iiiiffff ((((ssss////\\\\\\\\$$$$////////)))) {{{{
                   $$$$____ ....==== <<<<>>>>;;;;
                   rrrreeeeddddoooo uuuunnnnlllleeeessssssss eeeeooooffff(((())));;;;
               }}}}
               #### nnnnoooowwww pppprrrroooocccceeeessssssss $$$$____
           }}}}

       which is Perl short-hand for the more explicitly written
       version:






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           LLLLIIIINNNNEEEE:::: wwwwhhhhiiiilllleeee (((($$$$lllliiiinnnneeee ==== <<<<AAAARRRRGGGGVVVV>>>>)))) {{{{
               cccchhhhoooommmmpppp(((($$$$lllliiiinnnneeee))));;;;
               iiiiffff (((($$$$lllliiiinnnneeee ====~~~~ ssss////\\\\\\\\$$$$////////)))) {{{{
                   $$$$lllliiiinnnneeee ....==== <<<<AAAARRRRGGGGVVVV>>>>;;;;
                   rrrreeeeddddoooo LLLLIIIINNNNEEEE uuuunnnnlllleeeessssssss eeeeooooffff(((())));;;; #### nnnnooootttt eeeeooooffff((((AAAARRRRGGGGVVVV))))!!!!
               }}}}
               #### nnnnoooowwww pppprrrroooocccceeeessssssss $$$$lllliiiinnnneeee
           }}}}

       Or here's a a simpleminded Pascal comment stripper
       (warning: assumes no { or } in strings)

           LLLLIIIINNNNEEEE:::: wwwwhhhhiiiilllleeee ((((<<<<SSSSTTTTDDDDIIIINNNN>>>>)))) {{{{
               wwwwhhhhiiiilllleeee ((((ssss||||(((({{{{....****}}}}....****)))){{{{....****}}}}||||$$$$1111 ||||)))) {{{{}}}}
               ssss||||{{{{....****}}}}|||| ||||;;;;
               iiiiffff ((((ssss||||{{{{....****|||| ||||)))) {{{{
                   $$$$ffffrrrroooonnnntttt ==== $$$$____;;;;
                   wwwwhhhhiiiilllleeee ((((<<<<SSSSTTTTDDDDIIIINNNN>>>>)))) {{{{
                       iiiiffff ((((////}}}}////)))) {{{{      #### eeeennnndddd ooooffff ccccoooommmmmmmmeeeennnntttt????
                           ssss||||^^^^||||$$$$ffffrrrroooonnnntttt{{{{||||;;;;
                           rrrreeeeddddoooo LLLLIIIINNNNEEEE;;;;
                       }}}}
                   }}}}
               }}}}
               pppprrrriiiinnnntttt;;;;
           }}}}

       Note that if there were a ccccoooonnnnttttiiiinnnnuuuueeee block on the above
       code, it would get executed even on discarded lines.

       If the word wwwwhhhhiiiilllleeee is replaced by the word uuuunnnnttttiiiillll, the sense
       of the test is reversed, but the conditional is still
       tested before the first iteration.

       In either the iiiiffff or the wwwwhhhhiiiilllleeee statement, you may replace
       "(EXPR)" with a BLOCK, and the conditional is true if the
       value of the last statement in that block is true.  While
       this "feature" continues to work in version 5, it has been
       deprecated, so please change any occurrences of "if BLOCK"
       to "if (do BLOCK)".

       FFFFoooorrrr LLLLooooooooppppssss

       Perl's C-style ffffoooorrrr loop works exactly like the
       corresponding wwwwhhhhiiiilllleeee loop; that means that this:

           ffffoooorrrr (((($$$$iiii ==== 1111;;;; $$$$iiii <<<< 11110000;;;; $$$$iiii++++++++)))) {{{{
               ............
           }}}}

       is the same as this:






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           $$$$iiii ==== 1111;;;;
           wwwwhhhhiiiilllleeee (((($$$$iiii <<<< 11110000)))) {{{{
               ............
           }}}} ccccoooonnnnttttiiiinnnnuuuueeee {{{{
               $$$$iiii++++++++;;;;
           }}}}

       Besides the normal array index looping, ffffoooorrrr can lend
       itself to many other interesting applications.  Here's one
       that avoids the problem you get into if you explicitly
       test for end-of-file on an interactive file descriptor
       causing your program to appear to hang.

           $$$$oooonnnn____aaaa____ttttttttyyyy ==== ----tttt SSSSTTTTDDDDIIIINNNN &&&&&&&& ----tttt SSSSTTTTDDDDOOOOUUUUTTTT;;;;
           ssssuuuubbbb pppprrrroooommmmpppptttt {{{{ pppprrrriiiinnnntttt """"yyyyeeeessss???? """" iiiiffff $$$$oooonnnn____aaaa____ttttttttyyyy }}}}
           ffffoooorrrr (((( pppprrrroooommmmpppptttt(((())));;;; <<<<SSSSTTTTDDDDIIIINNNN>>>>;;;; pppprrrroooommmmpppptttt(((()))) )))) {{{{
               #### ddddoooo ssssoooommmmeeeetttthhhhiiiinnnngggg
           }}}}


       FFFFoooorrrreeeeaaaacccchhhh LLLLooooooooppppssss

       The ffffoooorrrreeeeaaaacccchhhh loop iterates over a normal list value and
       sets the variable VAR to be each element of the list in
       turn.  The variable is implicitly local to the loop and
       regains its former value upon exiting the loop.  If the
       variable was previously declared with mmmmyyyy, it uses that
       variable instead of the global one, but it's still
       localized to the loop.  This can cause problems if you
       have subroutine or format declarations within that block's
       scope.

       The ffffoooorrrreeeeaaaacccchhhh keyword is actually a synonym for the ffffoooorrrr
       keyword, so you can use ffffoooorrrreeeeaaaacccchhhh for readability or ffffoooorrrr for
       brevity.  If VAR is omitted, $$$$____ is set to each value.  If
       LIST is an actual array (as opposed to an expression
       returning a list value), you can modify each element of
       the array by modifying VAR inside the loop.  That's
       because the ffffoooorrrreeeeaaaacccchhhh loop index variable is an implicit
       alias for each item in the list that you're looping over.

       Examples:

           ffffoooorrrr ((((@@@@aaaarrrryyyy)))) {{{{ ssss////ffffoooooooo////bbbbaaaarrrr//// }}}}

           ffffoooorrrreeeeaaaacccchhhh $$$$eeeelllleeeemmmm ((((@@@@eeeelllleeeemmmmeeeennnnttttssss)))) {{{{
               $$$$eeeelllleeeemmmm ****==== 2222;;;;
           }}}}

           ffffoooorrrr $$$$ccccoooouuuunnnntttt ((((11110000,,,,9999,,,,8888,,,,7777,,,,6666,,,,5555,,,,4444,,,,3333,,,,2222,,,,1111,,,,''''BBBBOOOOOOOOMMMM'''')))) {{{{
               pppprrrriiiinnnntttt $$$$ccccoooouuuunnnntttt,,,, """"\\\\nnnn"""";;;; sssslllleeeeeeeepppp((((1111))));;;;
           }}}}

           ffffoooorrrr ((((1111........11115555)))) {{{{ pppprrrriiiinnnntttt """"MMMMeeeerrrrrrrryyyy CCCChhhhrrrriiiissssttttmmmmaaaassss\\\\nnnn"""";;;; }}}}



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           ffffoooorrrreeeeaaaacccchhhh $$$$iiiitttteeeemmmm ((((sssspppplllliiiitttt((((////::::[[[[\\\\\\\\\\\\nnnn::::]]]]****////,,,, $$$$EEEENNNNVVVV{{{{TTTTEEEERRRRMMMMCCCCAAAAPPPP}}}})))))))) {{{{
               pppprrrriiiinnnntttt """"IIIItttteeeemmmm:::: $$$$iiiitttteeeemmmm\\\\nnnn"""";;;;
           }}}}

       Here's how a C programmer might code up a particular
       algorithm in Perl:

           ffffoooorrrr (((($$$$iiii ==== 0000;;;; $$$$iiii <<<< @@@@aaaarrrryyyy1111;;;; $$$$iiii++++++++)))) {{{{
               ffffoooorrrr (((($$$$jjjj ==== 0000;;;; $$$$jjjj <<<< @@@@aaaarrrryyyy2222;;;; $$$$jjjj++++++++)))) {{{{
                   iiiiffff (((($$$$aaaarrrryyyy1111[[[[$$$$iiii]]]] >>>> $$$$aaaarrrryyyy2222[[[[$$$$jjjj]]]])))) {{{{
                       llllaaaasssstttt;;;; #### ccccaaaannnn''''tttt ggggoooo ttttoooo oooouuuutttteeeerrrr ::::----((((
                   }}}}
                   $$$$aaaarrrryyyy1111[[[[$$$$iiii]]]] ++++==== $$$$aaaarrrryyyy2222[[[[$$$$jjjj]]]];;;;
               }}}}
               #### tttthhhhiiiissss iiiissss wwwwhhhheeeerrrreeee tttthhhhaaaatttt llllaaaasssstttt ttttaaaakkkkeeeessss mmmmeeee
           }}}}

       Whereas here's how a Perl programmer more confortable with
       the idiom might do it:

           OOOOUUUUTTTTEEEERRRR:::: ffffoooorrrreeeeaaaacccchhhh $$$$wwwwiiiidddd ((((@@@@aaaarrrryyyy1111)))) {{{{
           IIIINNNNNNNNEEEERRRR::::   ffffoooorrrreeeeaaaacccchhhh $$$$jjjjeeeetttt ((((@@@@aaaarrrryyyy2222)))) {{{{
                       nnnneeeexxxxtttt OOOOUUUUTTTTEEEERRRR iiiiffff $$$$wwwwiiiidddd >>>> $$$$jjjjeeeetttt;;;;
                       $$$$wwwwiiiidddd ++++==== $$$$jjjjeeeetttt;;;;
                    }}}}
                 }}}}

       See how much easier this is?  It's cleaner, safer, and
       faster.  It's cleaner because it's less noisy.  It's safer
       because if code gets added between the inner and outer
       loops later on, the new code won't be accidentally
       excecuted:  the nnnneeeexxxxtttt explicitly iterates the other loop
       rather than merely terminating the inner one.  And it's
       faster because Perl executes a ffffoooorrrreeeeaaaacccchhhh statement more
       rapidly than it would the equivalent ffffoooorrrr loop.

       BBBBaaaassssiiiicccc BBBBLLLLOOOOCCCCKKKKssss aaaannnndddd SSSSwwwwiiiittttcccchhhh SSSSttttaaaatttteeeemmmmeeeennnnttttssss

       A BLOCK by itself (labeled or not) is semantically
       equivalent to a loop that executes once.  Thus you can use
       any of the loop control statements in it to leave or
       restart the block.  (Note that this is _N_O_T true in eeeevvvvaaaallll{{{{}}}},
       ssssuuuubbbb{{{{}}}}, or contrary to popular belief ddddoooo{{{{}}}} blocks, which do
       _N_O_T count as loops.)  The ccccoooonnnnttttiiiinnnnuuuueeee block is optional.

       The BLOCK construct is particularly nice for doing case
       structures.

           SSSSWWWWIIIITTTTCCCCHHHH:::: {{{{
               iiiiffff ((((////^^^^aaaabbbbcccc////)))) {{{{ $$$$aaaabbbbcccc ==== 1111;;;; llllaaaasssstttt SSSSWWWWIIIITTTTCCCCHHHH;;;; }}}}
               iiiiffff ((((////^^^^ddddeeeeffff////)))) {{{{ $$$$ddddeeeeffff ==== 1111;;;; llllaaaasssstttt SSSSWWWWIIIITTTTCCCCHHHH;;;; }}}}
               iiiiffff ((((////^^^^xxxxyyyyzzzz////)))) {{{{ $$$$xxxxyyyyzzzz ==== 1111;;;; llllaaaasssstttt SSSSWWWWIIIITTTTCCCCHHHH;;;; }}}}
               $$$$nnnnooootttthhhhiiiinnnngggg ==== 1111;;;;
           }}}}



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       There is no official switch statement in Perl, because
       there are already several ways to write the equivalent.
       In addition to the above, you could write

           SSSSWWWWIIIITTTTCCCCHHHH:::: {{{{
               $$$$aaaabbbbcccc ==== 1111,,,, llllaaaasssstttt SSSSWWWWIIIITTTTCCCCHHHH  iiiiffff ////^^^^aaaabbbbcccc////;;;;
               $$$$ddddeeeeffff ==== 1111,,,, llllaaaasssstttt SSSSWWWWIIIITTTTCCCCHHHH  iiiiffff ////^^^^ddddeeeeffff////;;;;
               $$$$xxxxyyyyzzzz ==== 1111,,,, llllaaaasssstttt SSSSWWWWIIIITTTTCCCCHHHH  iiiiffff ////^^^^xxxxyyyyzzzz////;;;;
               $$$$nnnnooootttthhhhiiiinnnngggg ==== 1111;;;;
           }}}}

       (That's actually not as strange as it looks once you
       realize that you can use loop control "operators" within
       an expression,  That's just the normal C comma operator.)

       or

           SSSSWWWWIIIITTTTCCCCHHHH:::: {{{{
               ////^^^^aaaabbbbcccc//// &&&&&&&& ddddoooo {{{{ $$$$aaaabbbbcccc ==== 1111;;;; llllaaaasssstttt SSSSWWWWIIIITTTTCCCCHHHH;;;; }}}};;;;
               ////^^^^ddddeeeeffff//// &&&&&&&& ddddoooo {{{{ $$$$ddddeeeeffff ==== 1111;;;; llllaaaasssstttt SSSSWWWWIIIITTTTCCCCHHHH;;;; }}}};;;;
               ////^^^^xxxxyyyyzzzz//// &&&&&&&& ddddoooo {{{{ $$$$xxxxyyyyzzzz ==== 1111;;;; llllaaaasssstttt SSSSWWWWIIIITTTTCCCCHHHH;;;; }}}};;;;
               $$$$nnnnooootttthhhhiiiinnnngggg ==== 1111;;;;
           }}}}

       or formatted so it stands out more as a "proper" switch
       statement:

           SSSSWWWWIIIITTTTCCCCHHHH:::: {{{{
               ////^^^^aaaabbbbcccc////      &&&&&&&& ddddoooo {{{{
                                   $$$$aaaabbbbcccc ==== 1111;;;;
                                   llllaaaasssstttt SSSSWWWWIIIITTTTCCCCHHHH;;;;
                              }}}};;;;

               ////^^^^ddddeeeeffff////      &&&&&&&& ddddoooo {{{{
                                   $$$$ddddeeeeffff ==== 1111;;;;
                                   llllaaaasssstttt SSSSWWWWIIIITTTTCCCCHHHH;;;;
                              }}}};;;;

               ////^^^^xxxxyyyyzzzz////      &&&&&&&& ddddoooo {{{{
                                   $$$$xxxxyyyyzzzz ==== 1111;;;;
                                   llllaaaasssstttt SSSSWWWWIIIITTTTCCCCHHHH;;;;
                               }}}};;;;
               $$$$nnnnooootttthhhhiiiinnnngggg ==== 1111;;;;
           }}}}

       or

           SSSSWWWWIIIITTTTCCCCHHHH:::: {{{{
               ////^^^^aaaabbbbcccc//// aaaannnndddd $$$$aaaabbbbcccc ==== 1111,,,, llllaaaasssstttt SSSSWWWWIIIITTTTCCCCHHHH;;;;
               ////^^^^ddddeeeeffff//// aaaannnndddd $$$$ddddeeeeffff ==== 1111,,,, llllaaaasssstttt SSSSWWWWIIIITTTTCCCCHHHH;;;;
               ////^^^^xxxxyyyyzzzz//// aaaannnndddd $$$$xxxxyyyyzzzz ==== 1111,,,, llllaaaasssstttt SSSSWWWWIIIITTTTCCCCHHHH;;;;
               $$$$nnnnooootttthhhhiiiinnnngggg ==== 1111;;;;
           }}}}




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       or even, horrors,

           iiiiffff ((((////^^^^aaaabbbbcccc////))))
               {{{{ $$$$aaaabbbbcccc ==== 1111 }}}}
           eeeellllssssiiiiffff ((((////^^^^ddddeeeeffff////))))
               {{{{ $$$$ddddeeeeffff ==== 1111 }}}}
           eeeellllssssiiiiffff ((((////^^^^xxxxyyyyzzzz////))))
               {{{{ $$$$xxxxyyyyzzzz ==== 1111 }}}}
           eeeellllsssseeee
               {{{{ $$$$nnnnooootttthhhhiiiinnnngggg ==== 1111 }}}}

       A common idiom for a switch statement is to use ffffoooorrrreeeeaaaacccchhhh's
       aliasing to make a temporary assignment to $$$$____ for
       convenient matching:

           SSSSWWWWIIIITTTTCCCCHHHH:::: ffffoooorrrr (((($$$$wwwwhhhheeeerrrreeee)))) {{{{
                       ////IIIInnnn CCCCaaaarrrrdddd NNNNaaaammmmeeeessss////     &&&&&&&& ddddoooo {{{{ ppppuuuusssshhhh @@@@ffffllllaaaaggggssss,,,, ''''----eeee'''';;;; llllaaaasssstttt;;;; }}}};;;;
                       ////AAAAnnnnyyyywwwwhhhheeeerrrreeee////          &&&&&&&& ddddoooo {{{{ ppppuuuusssshhhh @@@@ffffllllaaaaggggssss,,,, ''''----hhhh'''';;;; llllaaaasssstttt;;;; }}}};;;;
                       ////IIIInnnn RRRRuuuulllliiiinnnnggggssss////        &&&&&&&& ddddoooo {{{{                    llllaaaasssstttt;;;; }}}};;;;
                       ddddiiiieeee """"uuuunnnnkkkknnnnoooowwwwnnnn vvvvaaaalllluuuueeee ffffoooorrrr ffffoooorrrrmmmm vvvvaaaarrrriiiiaaaabbbblllleeee wwwwhhhheeeerrrreeee:::: ````$$$$wwwwhhhheeeerrrreeee''''"""";;;;
                   }}}}

       Another interesting approach to a switch statement is
       arrange for a ddddoooo block to return the proper value:

           $$$$aaaammmmooooddddeeee ==== ddddoooo {{{{
               iiiiffff     (((($$$$ffffllllaaaagggg &&&& OOOO____RRRRDDDDOOOONNNNLLLLYYYY)))) {{{{ """"rrrr"""" }}}}
               eeeellllssssiiiiffff  (((($$$$ffffllllaaaagggg &&&& OOOO____WWWWRRRROOOONNNNLLLLYYYY)))) {{{{ (((($$$$ffffllllaaaagggg &&&& OOOO____AAAAPPPPPPPPEEEENNNNDDDD)))) ???? """"aaaa"""" :::: """"wwww"""" }}}}
               eeeellllssssiiiiffff  (((($$$$ffffllllaaaagggg &&&& OOOO____RRRRDDDDWWWWRRRR))))   {{{{
                   iiiiffff (((($$$$ffffllllaaaagggg &&&& OOOO____CCCCRRRREEEEAAAATTTT))))  {{{{ """"wwww++++"""" }}}}
                   eeeellllsssseeee                  {{{{ (((($$$$ffffllllaaaagggg &&&& OOOO____AAAAPPPPPPPPEEEENNNNDDDD)))) ???? """"aaaa++++"""" :::: """"rrrr++++"""" }}}}
               }}}}
           }}}};;;;


       GGGGoooottttoooo

       Although not for the faint of heart, Perl does support a
       ggggoooottttoooo statement.  A loop's LABEL is not actually a valid
       target for a ggggoooottttoooo; it's just the name of the loop.  There
       are three forms: goto-LABEL, goto-EXPR, and goto-&NAME.

       The goto-LABEL form finds the statement labeled with LABEL
       and resumes execution there.  It may not be used to go
       into any construct that requires initialization, such as a
       subroutine or a foreach loop.  It also can't be used to go
       into a construct that is optimized away.  It can be used
       to go almost anywhere else within the dynamic scope,
       including out of subroutines, but it's usually better to
       use some other construct such as last or die.  The author
       of Perl has never felt the need to use this form of goto
       (in Perl, that is--C is another matter).

       The goto-EXPR form expects a label name, whose scope will



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       be resolved dynamically.  This allows for computed gotos
       per FORTRAN, but isn't necessarily recommended if you're
       optimizing for maintainability:

           ggggoooottttoooo ((((""""FFFFOOOOOOOO"""",,,, """"BBBBAAAARRRR"""",,,, """"GGGGLLLLAAAARRRRCCCCHHHH""""))))[[[[$$$$iiii]]]];;;;

       The goto-&NAME form is highly magical, and substitutes a
       call to the named subroutine for the currently running
       subroutine.  This is used by _A_U_T_O_L_O_A_D_(_) subroutines that
       wish to load another subroutine and then pretend that the
       other subroutine had been called in the first place
       (except that any modifications to @@@@____ in the current
       subroutine are propagated to the other subroutine.)  After
       the ggggoooottttoooo, not even _c_a_l_l_e_r_(_) will be able to tell that this
       routine was called first.

       In almost all cases like this, it's usually a far, far
       better idea to use the structured control flow mechanisms
       of nnnneeeexxxxtttt, llllaaaasssstttt, or rrrreeeeddddoooo instead of resorting to a ggggoooottttoooo.
       For certain applications, the catch and throw pair of
       eeeevvvvaaaallll{{{{}}}} and _d_i_e_(_) for exception processing can also be a
       prudent approach.

       PPPPOOOODDDDssss:::: EEEEmmmmbbbbeeeeddddddddeeeedddd DDDDooooccccuuuummmmeeeennnnttttaaaattttiiiioooonnnn

       Perl has a mechanism for intermixing documentation with
       source code.  While it's expecting the beginning of a new
       statement, if the compiler encounters a line that begins
       with an equal sign and a word, like this

           ====hhhheeeeaaaadddd1111 HHHHeeeerrrreeee TTTThhhheeeerrrreeee BBBBeeee PPPPooooddddssss!!!!

       Then that text and all remaining text up through and
       including a line beginning with ====ccccuuuutttt will be ignored.  The
       format of the intervening text is described in the _p_e_r_l_p_o_d
       manpage.

       This allows you to intermix your source code and your
       documentation text freely, as in

           ====iiiitttteeeemmmm ssssnnnnaaaazzzzzzzzlllleeee(((($$$$))))

           TTTThhhheeee ssssnnnnaaaazzzzzzzzlllleeee(((()))) ffffuuuunnnnccccttttiiiioooonnnn wwwwiiiillllllll bbbbeeeehhhhaaaavvvveeee iiiinnnn tttthhhheeee mmmmoooosssstttt ssssppppeeeeccccttttaaaaccccuuuullllaaaarrrr
           ffffoooorrrrmmmm tttthhhhaaaatttt yyyyoooouuuu ccccaaaannnn ppppoooossssssssiiiibbbbllllyyyy iiiimmmmaaaaggggiiiinnnneeee,,,, nnnnooootttt eeeevvvveeeennnn eeeexxxxcccceeeeppppttttiiiinnnngggg
           ccccyyyybbbbeeeerrrrnnnneeeettttiiiicccc ppppyyyyrrrrooootttteeeecccchhhhnnnniiiiccccssss....

           ====ccccuuuutttt bbbbaaaacccckkkk ttttoooo tttthhhheeee ccccoooommmmppppiiiilllleeeerrrr,,,, nnnnuuuuffffffff ooooffff tttthhhhiiiissss ppppoooodddd ssssttttuuuuffffffff!!!!

           ssssuuuubbbb ssssnnnnaaaazzzzzzzzlllleeee(((($$$$)))) {{{{
               mmmmyyyy $$$$tttthhhhiiiinnnnggggiiiieeee ==== sssshhhhiiiifffftttt;;;;
               ....................................
           }}}}

       Note that pod translators should only look at paragraphs



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       beginning with a pod diretive (it makes parsing easier),
       whereas the compiler actually knows to look for pod
       escapes even in the middle of a paragraph.  This means
       that the following secret stuff will be ignored by both
       the compiler and the translators.

           $$$$aaaa====3333;;;;
           ====sssseeeeccccrrrreeeetttt ssssttttuuuuffffffff
            wwwwaaaarrrrnnnn """"NNNNeeeeiiiitttthhhheeeerrrr PPPPOOOODDDD nnnnoooorrrr CCCCOOOODDDDEEEE!!!!????""""
           ====ccccuuuutttt bbbbaaaacccckkkk
           pppprrrriiiinnnntttt """"ggggooootttt $$$$aaaa\\\\nnnn"""";;;;

       You probably shouldn't rely upon the _w_a_r_n_(_) being podded
       out forever.  Not all pod translators are well-behaved in
       this regard, and perhaps the compiler will become pickier.










































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