http://perl-begin.org/tutorials/perl-for-newbies/ is offered into the public domain (cc zero)

http://www.ignition-training.com/booklets/perldistilled.pdf is Creative Commons - attribution, no derivatives (cc by-nd 3.0) which means commercial use is acceptable.

The perldoc tutorials are released under the same license as perl itself.

I'm not immediately aware of others with an explicitly commercial-okay license for gratis. I wish more lists of tutorials and books listed the licenses with the other details.

Beyond those there are a good many for personal non-commercial use one could encourage others to download for more information. Also, if it's for work there shouldn't be a problem buying a copy of materials for each person unless it's a very small business or this has no manager approval.