I stand corrected. I had forgotten (or maybe never read) that part. The full details in perlrun are much too long to quote, but here's one relevant passage:

If the #! line does not contain the word "perl", the program named after the #! is executed instead of the Perl interpreter. This is slightly bizarre, but it helps people on machines that don't do #!, because they can tell a program that their SHELL is /usr/bin/perl, and Perl will then dispatch the program to the correct interpreter for them.