Punctuation variables (and their English.pm equivalents) are global variables. Messing with globals is dangerous in a complex program as it can lead to very subtle and hard to fix bugs. If you must change a magic variable in a non-trivial program, do it in a local scope.

For example, to slurp a filehandle into a scalar, it's common to set the record separator to undef instead of a newline. If you choose to do this (instead of using the File::Slurp manpage!) then be sure to localize the global and change it for as short a time as possible.

   # BAD:
   $/ = undef;
   my $content = <$fh>;
   # BETTER:
   my $content;
       local $/ = undef;
       $content = <$fh>;
   # A popular idiom:
   my $content = do { local $/ = undef; <$fh> };


The current PPI (v1.118) has a bug where $^ variables absorb following whitespace by mistake. This makes it harder to spot those as magic variables. Hopefully this will be fixed by PPI 1.200. In the meantime, we have a workaround in this module.

Additionally, PPI v1.118 fails to recognize %! and %^H as magic variables. PPI instead sees the ``%'' as a modulus operator. We have no workaround for that bug right now.


Initial development of this policy was supported by a grant from the Perl Foundation.


Chris Dolan <cdolan@cpan.org>


Copyright (c) 2007 Chris Dolan. Many rights reserved.

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself. The full text of this license can be found in the LICENSE file included with this module.