If you're looking for perfect cubes ....

use POSIX qw(ceil floor);

if (ceil($num ** 1/3) == floor($num ** 1/3)) {

print $num . " is a cube of " $num ** 1/3;

} else {

print $num . " is not a perfect cube.";

}
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Like all of my code the above is untested and comes with no warrenty implied or otherwise.