Malcolm Beattie's B module allows you to examine the Perl op tree at runtime, in Perl space; it's the basis of the Perl compiler. But what it doesn't let you do is manipulate that op tree: it won't let you create new ops, or modify old ones. Now you can. Well, if you're intimately familiar with Perl's internals, you can. WWW: http://search.cpan.org/dist/B-Generate/