Did a quick and dirty scan of CPAN to see which licenses are actually used by perl modules. The license field in the metadata is supposed to contain one (or multiple) of these strings: https://metacpan.org/pod/CPAN::Meta::Spec#license

My scan found this (including 767 distributions where the license field was null instead of a string):

16561 perl_5
7395 perl
3160 unknown
2656 artistic_2
1148 mit
767 <NULL>
758 bsd
472 gpl_3
465 open_source
404 apache_2_0
361 gpl
210 gpl_2
138 unrestricted
137 lgpl_2_1
122 freebsd
95 artistic_1
79 artistic
68 lgpl
49 gpl_1
46 apache
44 agpl_3
37 Perl
35 gplv2
33 lgpl_3_0
33 MIT
23 artistic2
20 gpl2
19 Artistic_2_0
14 gpl3
13 http://dev.perl.org/licenses/
12 GPL
9 restricted
8 LGPL
7 cc0
7 GPLv2
7 BSD
7 GPL version 2
5 restrictive
4 apache2
3 CC0
3 perl, lgpl
3 nil
3 zlib
3 wtfpl
3 Artistic License 2.0
2 x11
2 mozilla
2 gnu
2 mozilla_1_1
2 artistc
2 Perl Artistic
2 MIT-License
2 GPL_3
2 http://hop.perl.plover.com/Examples/LICENSE.txt
2 lgpl3
2 Fermitools
2 Artistic
1 Public Domain
1 Apache_2_0
1 cpal
1 public domain
1 Apache License, Version 2.0
1 This program is free software; you can redistribute it and/or modify it
1 perl5
1 cecill
1 GPLv3
1 GPL Version 2
1 ISC
1 MPL
1 agpl
1 Other
1 artistic, gpl2+
1 GPLv2+
1 GPL2
1 Software::License::GPL_3
1 GPL-2
1 CPAL
1 artistic/GPL
1 eclipse
1 apache_1_1
1 AGPL # https://www.gnu.org/licenses/license-list.html#GNUGPL
1 Standard-Perl
1 cpl
1 AGPL_3

#perl #cpan