• Perl can now handle binary data correctly and has functions to
  pack and unpack binary structures into
  arrays or lists. You can now do arbitrary ioctl functions.
• You can now pass things to subroutines by reference.
• Debugger enhancements.
• An array or associative array may now appear in a local()
  list.
• Array values may now be interpolated into strings.
• Subroutine names are now distinguished by prefixing with
  &. You can call subroutines without using do,
  and without passing any argument list at all.
• You can use the new -u switch to cause perl to dump
  core so that you can run undump and produce a binary
  executable image. Alternately you can use the "dump"
  operator after initializing any variables and such.
• You can now chop lists.
• Perl now uses /bin/csh to do filename globbing,
  if available. This means that filenames with spaces or other
  strangenesses work right.
• New functions: mkdir and rmdir,
  getppid, getpgrp and setpgrp,
  getpriority and setpriority,
  chroot, ioctl and fcntl,
  flock, readlink, lstat,
  rindex, pack and unpack,
  read, warn, dbmopen and
  dbmclose, dump, reverse,
  defined, undef.

(Quelle)