Where is Perl?

It's not so easy to know who or what uses Perl: it's so well integrated that it's often invisible to the end user (no .asp or .php betraying its use, for instance) and the language is mature enough that authors or publishers do not mention they used it. Also, it's not customary to prefix the name of large programs with the language name, as with PHP.

O'Reilly keeps a list of success stories on its web site, that can be attributed in part to the qualities of Perl, its libraries and its developer community: Perl success stories

Companies using Perl

A lot of well-known companies use Perl, internaly or for high traffic web sites:

Applications

A few programs written in Perl: