If i remember corectly KOHA is a library management tool with MARC files support and a impressive list of features, and written in Perl !

Project homepage is at http://savannah.nongnu.org/projects/koha/ and there's a website at http://www.koha.org/.

HTH
secret.

Update: Regarding kulls post (just above mine ;) i can confirm koha is Perl only since that's how i heard about it in the first place .