You are attempting to use nroff macros in your 'manpage' that are not defined on your system, it could be that your man has not properly installed the mdoc or mandoc macros or your nroff is not installed. Either way it has nothing to do with Perl and you should be asking somewhere specific to your OS.

If you are creating manpages for Perl programs then you are better using POD and pod2man - this also has the benefit of allowing other formatters such as HTML.

/J\