Most of these things also apply to any programming task in any language not just Perl. At a first glance the only thing that doesn't fit into any language is "Are you using the right special variable?".
Comment on Re: brian's Guide to Solving Any Perl Problem
There is also the Perl pragma's, using perldoc, several mentions of the perl documentation, using Data::Dumper, using the perl debugger, checking module versions, setting the environment in %ENV, using Test::Harness, and probably a few other things. :)