+=head2 C<license_c2g @licenses>
+
+Maps F<META.yml> C<license> tag values to the corresponding list of Gentoo licenses identifiers.
+Duplicates are stripped off.
+
+The included data was gathered from L<Module::Install> and L<Software::License>.
+
+=cut
+
+my %licenses = (
+ apache => [ 'Apache-2.0' ],
+ artistic => [ 'Artistic' ],
+ artistic_2 => [ 'Artistic-2' ],
+ bsd => [ 'BSD' ],
+ gpl => [ 'GPL-1' ],
+ gpl2 => [ 'GPL-2' ],
+ gpl3 => [ 'GPL-3' ],
+ lgpl => [ 'LGPL-2.1' ],
+ lgpl2 => [ 'LGPL-2.1' ],
+ lgpl3 => [ 'LGPL-3' ],
+ mit => [ 'MIT' ],
+ mozilla => [ 'MPL-1.1' ],
+ perl => [ 'Artistic', 'GPL-2' ],
+);
+
+sub license_c2g {
+ my %seen;
+ grep !$seen{$_}++, map @{$licenses{+lc} || []}, @_;
+}
+