use warnings;
use subs qw(non_commutative); #necessary

$x = 10 * non_commutative;
$y = non_commutative * 10;

print "$x\n$y\n\n";

$x = 10 + non_commutative;
$y = non_commutative + 10;

print "$x\n$y\n";

sub non_commutative {return 17}

__END__
Outputs:
170
17

27
17