Do you know a more reliable solution, other than constructing optrees by hand?

I don't need one, I manage to avoid writing subroutines that clash with classes, pretty much the same way most of CPAN and everyone else seems to, fairly easily :)

Although this might be a candidate :) subs::auto - Read barewords as subroutine names.

This pragma lexically enables the parsing of any bareword as a subroutine name, except those which corresponds to an entry in %INC (expected to be class names) or whose symbol table entry has an IO slot (expected to be filehandles).