People often talk about PSI::ESP: a powerful module that cannot be downloaded from CPAN but must instead be earned by experience.
As part of one of his Perl tutorials at IBM DeveloperWorks Teodor Zlatanov demonstrates an implementation of the PSI::ESP module.
DeveloperWorks also has several other good articles by the same author as well as other Perl related articles.
My addition to the prescience of this module would be: "binmode() the filehandle".
And yes, I knew you were soing to say that. ;-)