Rather than focus on specific modules, I would suggest researching certain technology areas e.g. web development, database access etc - depends on what your background is, and what type of job you are looking for.

Getting up to speed in these areas will provide a couple of benefits, including:

1. Transferable skills in areas such as HTML, CSS, SQL etc that don't necessarily rely on Perl as the underlying technology
2. Some expertise in Perl-specific solutions for these areas e.g. CGI::*, DBI::* and frameworks such as Catalyst