The <#2168#>block<#2168#> and <#2169#>return-from<#2169#> constructs provide a structured lexical
non-local exit facility. At any point lexically within a <#2170#>block<#2170#>
construct, a <#2171#>return-from<#2171#> with the same name may be used to
perform an immediate transfer of control that
exits from the <#2172#>block<#2172#>. In the most common cases this mechanism is
more efficient than the dynamic non-local exit facility
provided by <#2173#>catch<#2173#> and <#2174#>throw<#2174#>, described in
section~#CATCH-THROW-SECTION#2175>