Well I have the same problem with irc/irssi. First it tried to install glib20 although it's already installed then he pulls pcre in, although that one is also installed.
Code:
===> Compressing manual pages for pcre-8.31_1
===> Running ldconfig
/sbin/ldconfig -m /usr/local/lib
===> Registering installation for pcre-8.31_1
===> Returning to build of glib-2.28.8_4
Error: shared library "pcre.1" does not exist
*** Error code 1
Stop in /usr/ports/devel/glib20.
*** Error code 1
Stop in /usr/ports/devel/glib20.
*** Error code 1
Stop in /usr/ports/devel/glib20.