Counting ("for") loops and iterating ("foreach") loops can use the for and the foreach keywords interchangably, as documented in perlsyn.

Personally, I use "for" for counting ("for") loops, and "foreach" for iterating ("foreach") loops. Some people use "for" unconditionally because it is shorter.

Iterating ("foreach") loops: 

foreach my $ele (@array) { ... }
foreach (@array) { ... }
... foreach @array;
foreach my $item ($list_item_0, $list_item_1, $list_item_2) { ... }
foreach ($list_item_0, $list_item_1, $list_item_2) { ... }
... foreach $list_item_0, $list_item_1, $list_item_2;

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Also iterating ("foreach") loops: 

for my $ele (@array) { ... }
for (@array) { ... }
... foreach @array;
for my $item ($list_item_0, $list_item_1, $list_item_2) { ... }
for ($list_item_0, $list_item_1, $list_item_2) { ... }
... foreach $list_item_0, $list_item_1, $list_item_2;

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Counting ("for") loops: 

for (my $i = 0; $i < 10; $i++) { ... }
for my $i (0..9) { ... }      # *
for (0..9) { ... }            # *
... for 0..9;                 # *

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Also counting ("for") loops: 

foreach (my $i = 0; $i < 10; $i++) { ... }
foreach my $i (0..9) { ... }  # *
foreach (0..9) { ... }        # *
... foreach 0..9;             # *

[download]

* — Loops of the form for/foreach [...] ($num1..$num2) are optimized into a counting ("for") loop.

In reply to Re: for() or foreach() ? by ikegami
in thread for() or foreach() ? by abachus

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