First of all, just because someone charges for a software product doesn't mean it's good. Just like that open source doesn't mean it's good.

The only commercial Perl software I know of is a mud written in Perl, written by Thomas Boutell, the same person who wrote the GD library (the C library, not the Perl interface). However, there is commercial software out there of which at least pieces have been written in Perl. Veritas cluster software for instance. Solaris also comes with some tools written in Perl. Some HP Openview programs are written in Perl.

Abigail