How do I perform an operation on a series of integers?

To call a function on each element in an array, and collect the results, use: 

    @results = map { my_func($_) } @array;

For example: 

    @triple = map { 3 * $_ } @single;

To call a function on each element of an array, but ignore the results: 

    foreach $iterator (@array) {
        &my_func($iterator);
    }

To call a function on each integer in a (small) range, you can use: 

    @results = map { &my_func($_) } (5 .. 25);

but you should be aware that the .. operator creates an array of all integers in the range. This can take a lot of memory for large ranges. Instead use: 

    @results = ();
    for ($i=5; $i < 500_005; $i++) {
        push(@results, &my_func($i));
    }