Best way to iterate through a Perl array
In terms of speed: #1 and #4, but not by much in most instances.
You could write a benchmark to confirm, but I suspect you'll find #1 and #4 to be slightly faster because the iteration work is done in C instead of Perl, and no needless copying of the array elements occurs. (
$_is aliased to the element in #1, but #2 and #3 actually copy the scalars from the array.)#5 might be similar.
In terms memory usage: They're all the same except for #5.
for (@a)is special-cased to avoid flattening the array. The loop iterates over the indexes of the array.In terms of readability: #1.
In terms of flexibility: #1/#4 and #5.
#2 does not support elements that are false. #2 and #3 are destructive.
If you only care about the elements of @Array, use:
for my $el (@Array) {# ...}or
If the indices matter, use:
for my $i (0 .. $#Array) {# ...}Or, as of perl 5.12.1, you can use:
while (my ($i, $el) = each @Array) {# ...}If you need both the element and its index in the body of the loop, I would expect using each to be the fastest, but then you'll be giving up compatibility with pre-5.12.1 perls.
Some other pattern than these might be appropriate under certain circumstances.