1.6. Loops

foreach

C style for loops exist but you almost never need them in Perl. foreach is usually simpler.

Iterating over an array

my @array = ('a', 'b', 'c', 1, 2, 3);

foreach my $i (@array) {
    print $i;
}
# prints 'abc123'

Iterating over a hash

my %hash = (a => 1, b => 2, c => 3);

foreach my $i (keys %hash) {
    print $hash{$i};
}
# prints '123'

while

my $i = 0;

while ($i < 4) {
    print $i;
    $i++;
}
# prints '0123'

Postfix loops

Postfix notation exists for foreach, for, while, and until loops.

print $_ foreach ('a', 'b', 'c');
print $_ for     ('a', 'b', 'c');
# both statemets print 'abc'

last

Exit the loop immediately. This works with any kind of loop.

foreach my $i (@array) {
    print $i;
    last if $i > 3; # break out of the loop early
}

next

Start the next iteration of the loop immediately. This also works with any kind of loop.

foreach my $i (@array) {
    next if $i > 3; # don't print anything for $i > 3
    print $i;
}