"FWIW Perl4 had an aliasing feature ..."

Purely as an historical note, I do recall reading about that in the first Camel book. In perlhist:

Perl 4 introduced the first Camel book.  Really.  We mostly just
    switched version numbers so the book could refer to 4.000.

So that feature would have existed in Perl3. I don't have any information on which specific Perl version introduced it. I don't believe I used that feature in any version prior to Perl5.