I've posted working code (plz read again), build on this and you'll find your error. ( we are at a point were you should show more efforts ;-)

Beside of this, you are using an internal feature of Term::ReadLine::Perl while Term::ReadLine offers an official interface for all sub-modules.

I've tested it with the debugger setting env and either *::Gnu *::Perl and *::Zoid did tab-completion w/o problems.

Have a look at Attribs