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This is an excerpt from the latest version perlfaq4.pod, which
comes with the standard Perl distribution. These postings aim to
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4.8: 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,

@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) {

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

@results = map { some_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; $i++) {
push(@results, some_func($i));

This situation has been fixed in Perl5.005. Use of ".." in a "for" loop
will iterate over the range, without creating the entire range.

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

will not create a list of 500,000 integers.


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