phpman > perldoc > SERIES(1)

Found in /usr/share/perl/5.34/pod/perlfaq4.pod
  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:

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

    For example:

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

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

        foreach my $iterator (@array) {
            some_func($iterator);
        }

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

        my @results = map { some_func($_) } (5 .. 25);

    but you should be aware that in this form, the ".." operator creates a
    list of all integers in the range, which can take a lot of memory for
    large ranges. However, the problem does not occur when using ".." within
    a "for" loop, because in that case the range operator is optimized to
    *iterate* over the range, without creating the entire list. So

        my @results = ();
        for my $i (5 .. 500_005) {
            push(@results, some_func($i));
        }

    or even

       push(@results, some_func($_)) for 5 .. 500_005;

    will not create an intermediate list of 500,000 integers.