my %hash = (
    polygon => {
        abc => ["0, 0, 10, 0, 12, 2", "10, 10, 20, 10, 22, 12",],
        def => ["3, 5, 3, 8, 7, 10"],
    },
    rectangle => {
        abc => ["-10, -10, 20, 20"],
        def => ["22, 33, 44, 44", "1, 1, -3, -6"],
    }
);

##</code><code>##

for my $shape (sort keys %hash) {
    for my $class (sort keys %{$hash{$shape}}) {
        print <<LINE for @{$hash{$shape}{$class}};
<$shape class ="$class" coordinates="$_">
LINE
    }
}