In the case of Carp specifically there is a far easier way. Use Carp::Heavy. Then redefine Carp::longmess_heavy and Carp::shortmess_heavy.

Otherwise you'd have to walk the symbol table. Just to get you started on that, print out the keys of %main::. All of the keys ending in :: are subtables you can look for. Beware of infinite loops. (For instance %main::main::main:: is the same as %main::.)