$h{1, 2} = "hello";

##</code><code>##

my %h;
$h{1, 2} = "hello";
$Data::Dumper::Useqq = 1;
print Dumper \%h;

##</code><code>##

$SUBSCRIPT_SEPARATOR
$SUBSEP
$;      The subscript separator for multidimensional array emulation. If
        you refer to a hash element as

            $foo{$a,$b,$c}

        it really means

            $foo{join($;, $a, $b, $c)}