Does the foreach statement iterate in order or it might be random order?

Question

I was wondering if the foreach statement in Perl iterates the items in an array in consistent order? That is, do I get different results if I use foreach multiple times on the same array or list?

Answer 1

If you don't change the list in between times, it will alawys be in a consistent order.

Answer 2

Yes, items in a foreach statement are iterated in order.

Your question might arise from confusion over iterating over the elements of a hash:

my %hash = ('a' => 1, 'b' => 2, 'c' => 3);
foreach my $key (keys %hash) { print $key } ;    # output is "cab"

But the seemingly random order is an artifact of how data are stored in a Perl hash table (data in a Perl hash table are not ordered). It is the keys statement that is "changing" the order of the hash table, not the foreach.

Answer 3

The reasoning for why Perl's foreach loop hash ordering is seemingly random is in the perlsec document, linked here