but where do you actually declare them as references, using the slash operator?

You don't "declare" references -- they are just scalars with 'special content' -- you 'take references' when you need them.

In the case of the code, the references are taken when the subroutine is called:

 ... for fuzzyMatch( \$hay, \$nee, 3 );
#....................^......^
[download]

Ie. $hay & $nee are normal strings in the main program.

When I call fuzzyMatch( \ $hay, \ $nee, 3 ), I am taking references to those two strings (using '\') and passing them into the subroutine.

In the subroutine those references get assigned to the local variables: $rHay & $rNee respectively:

sub fuzzyMatch {
    my( $rHay, $rNee, $misses ) = @_;
    ...
[download]