Limitations in PL/perl

Folks,

Is there any documentation anywhere on what subset of Perl functionality is
supported by PL/perl?   I've had a lot of annoying trial-and-error sessions
lately where I'll try something that works on the command line only to find
out that it silently fails in PL/perl.

For example:
On the command line:
$some_text =~ s/\W|\s//g;
... works great to remove all punctuation and spaces in a string.

But in PL/perl, I have to use:
$some_text =~ s/[^A-Za-z0-9]/""/eg;

Or is this maybe a problem with the version of Perl installed on the DB
server?

Thanks for any help.

--
-Josh Berkus
 Aglio Database Solutions
 San Francisco