perl-tab-to-comment

perl-tab-to-comment is a variable defined in `perl-mode.el'.
Its value is

nil

Documentation:
Non-nil means TAB moves to eol or makes a comment in some cases.
For lines which don't need indenting, TAB either indents an
existing comment, moves to end-of-line, or if at end-of-line already,
create a new comment.

You can customize this variable.