Since Ruby 2.6, irb has been separated to gem. ${PREFIX}/bin/irb is installed by lang/ruby26 but it is a wrapper. To run irb properly, this gem is needed.
A commit references this bug: Author: meta Date: Tue May 14 01:42:49 UTC 2019 New revision: 501609 URL: https://svnweb.freebsd.org/changeset/ports/501609 Log: Add new port devel/rubygem-irb, Interactive Ruby Ruby 2.6 requires this gem port. ${PREFIX}/bin/irb installed by lang/ruby26 is just a wrapper script of this gem. PR: 237870 Submitted by: myself Differential Revision: https://reviews.freebsd.org/D20254 Changes: head/devel/Makefile head/devel/rubygem-irb/ head/devel/rubygem-irb/Makefile head/devel/rubygem-irb/distinfo head/devel/rubygem-irb/pkg-descr
Reporter is committer (and ruby@), assign accordingly.
Committed.