rpm54: add variant +perl5_28

* allow perl5 portgroup to determine the default variant
* ensure ossp-uuid uses the same variant

sysutils/rpm54/Portfile

@@ -1,6 +1,7 @@
 # -*- coding: utf-8; mode: tcl; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- vim:fenc=utf-8:ft=tcl:et:sw=4:ts=4:sts=4
 
 PortSystem          1.0
+PortGroup           active_variants 1.1
 PortGroup           perl5 1.0
 
 name                rpm54
@@ -61,12 +62,12 @@ extract.post_args   "| cpio -dvim"
 build.type          gnu
 
 # use perl5 port group to create variants to match dependency ossp-uuid
-# set default variant to perl5_24 (#52081)
+# ensure ossp-uuid uses same variant
 
 perl5.conflict_variants yes
-perl5.branches          5.26
-perl5.default_branch    5.26
+perl5.branches          5.26 5.28
 perl5.create_variants   ${perl5.branches}
+require_active_variants ossp-uuid ${perl5.variant}
 
 configure.args      --disable-nls \
                     --infodir=${prefix}/share/info \