mpersico has asked for the wisdom of the Perl Monks concerning the following question:

Just when I thought I had seen everything:
my %hash; my $foo = 'hello'; my $bar = 'world'; my $baz = 'folk'; $hash{ $foo, $bar, $baz } = '##eek what magic is this?'; print $hash{"$foo\x{1c}$bar\x{1c}$baz"};
##eek what magic is this?

By what rule are multiple variables, separated by a comma, turned into a string with a File Separator between the pieces? I mean if I squint hard enough, that expression for the key is a list, and then the list is "stringified" to be a key, in which case I would have expected a space (\x{20}) separated expression. Perl 5.16 and Perl 5.26.1