Previous versions (lang/perl5.2x) symlinked /usr/local/bin/perl5 to perl, but this link is missing from lang/perl5.30. If this is by designed then I think it should be mentioned when doing "pkg upgrade" because it breaks BWC.
The perl5 symlink was never a thing, it was a FreeBSD oddity. Before removing it, I checked most of the software in the ports tree using Perl, and none used "perl5", they either used "perl" or a computed "perlX.YY.Z". I have no idea what BWC is but it should probably be fixed instead.
BWC means "backward compatibility" (sorry, it seems that this is not a common way of writing it). The removed symlink is a problem for user-written scripts rather than ports.