fold_in

 This command allows you to enter the fold the cursor is currently on.
 If the fold is a virtual fold then AE will attempt to create a new buffer,
 load in the file, and select the nested buffer. The directory of the current
 file can be inherited to the nested virtual file.

 eg:   Currently In       Virtual fold line  Resulting File

       c:/docs/x.c        y.c                c:/docs/y.c

       c:/docs/x.c        d:y.c              d:y.c

       c:/docs/x.c        /y.c               c:/y.c

 On DOS and OS/2 $(ENVIRONMENT_VARIABLE) strings are expanded too.

 eg:   >>> $(INCLUDE)/sys/stat.h

       Loads up c:/include/sys/stat.h if INCLUDE=C:\INCLUDE.