How do I read two items at a time in a Perl foreach loop?

I'd use splice.

my @list = qw(1 2 3 4 5 6);
while(my ($i,$j) = splice(@list,0,2)) {
  print "i: $i, j: $j\n";
}

I believe the proper way to do this is to use natatime, from List::MoreUtils:

from the docs:

natatime BLOCK LIST

Creates an array iterator, for looping over an array in chunks of $n items at a time. (n at a time, get it?). An example is probably a better explanation than I could give in words.

Example:

 my @x = ('a' .. 'g');
 my $it = natatime 3, @x;
 while (my @vals = $it->())
 {
     print "@vals\n";
 }

This prints

a b c
d e f
g

The implementation of List::MoreUtils::natatime:

sub natatime ($@)
{
    my $n = shift;
    my @list = @_;

    return sub
    {
        return splice @list, 0, $n;
    }
}