During the build of x11-toolkits/pango, glib-mkenums from the devel/glib20 port
is executed.  However, glib-mkenums is a perl script, so we
need to specify "perl5" in USES.  This allows us to use perl to build this port,
without creating a runtime dependency on perl.

See:
http://lists.freebsd.org/pipermail/freebsd-ports/2006-December/037249.html

Specify:
USES = perl5
USE_PERL5 = build

to add perl5 to BUILD_DEPENDS and not RUN_DEPENDS for this port.