AFAIK even the most modern Perl 5.32 runs Perl 4 programs just fine, so "porting" programs from 4 to 5 was "trivial" in the strongest sense. Perl 7 finally is

AFAIK even the most modern Perl 5.32 runs Perl 4 programs just fine, so "porting" programs from 4 to 5 was "trivial" in the strongest sense. Perl 7 finally is going to break this compatibility, at least according to the current plan, but the "porting" still is supposed to be trivial, in most cases just adding a pragma or two. 27 years after Perl 5 was released...