In addition to Perlix (can't find a link) and the Perl shell which are discussed in The Perl Journal #18 (no longer on-line) there is Claudio Calavelli's file system written in Perl.

The thought of this hurts my brain even more than the thought of his INTERCAL compiler written in Perl.

John.
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And the eighth and final rule, if this is your first time using Perl, you will have to write code.