[bch]

This reminds me of finding out (the Hard Way) that Perl’s sort used internally[0] the same $a or $b that I happened to be using.

[0] https://perldoc.perl.org/functions/sort

If the subroutine's prototype is ($$), the elements to be compared are passed by reference in @_, as for a normal subroutine. This is slower than unprototyped subroutines, where the elements to be compared are passed into the subroutine as the package global variables $a and $b (see example below).