If you are having trouble with your “hello world” wxPerl script on Mac OS X, check your shebang (#!) line and make sure you’re running /usr/bin/wxPerl (or which ever wxPerl you have) rather than merely /usr/bin/perl — the normal perl will display the main window but won’t allow interaction between the window and the interface (e.g. you can see hello world but can’t click the button).
This posting seems to imply that Mac OS X 10.4 comes with a wxPerl installed; you can also get it via cpan / cpanp or from the wxPerl website if you don’t have it on your Mac.