Term::ReadLine::Perl doesn't pay attention to .inputrc files (at least I don't see it trying to do so looking through the source). Term::ReadLine::Gnu sits on top of the C readline library and probably would be more likely to honour your .inputrc.

Update: Term::ReadLine::readline which ::Perl uses apparently does pay some attention to .inputrc files. See Re: Term::ReadLine ignores .inputrc for more information.