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

Question

What I\'m looking for is something like:

@list = qw(1 2 3 4 5 6);
foreach (@list) {
  #perl magic goes here 
  print \"i: $i, j:$j\\n\";
}

Answer 1

This can be done non-destructively, with Eric Strom's simply fantastic List::Gen:

perl -MList::Gen=":utility" -E '@nums = "1" .. "6" ; 
      say "i:$_->[0] j:$_->[1]" for every 2 => @nums'

Output:

i:1 j:2 
i:3 j:4 
i:5 j:6 

Edit (add a CPAN-less version):

Array slices and C-style for loop à la brian d foy and Tom Christiansen! This can be read as "use an index ($i) to loop through a @list foreach $n elements at a time":

use v5.16; # for strict, warnings, say

my @list = "1" .. "6";
my $n = 2 ;   # the number to loop by
$n-- ;        # subtract 1 because of zero index

foreach (my $i = 0 ; $i < @list ; $i += $n ) { 
  say "i:", [ @list[$i..$i+$n] ]->[0], " j:", [ @list[$i..$i+$n] ]->[1];
  $i++ ;          
}

We access the results as elements (->[0]) of an anonymous array ([ ]). For more generic output the interpolated array slice could be used on its own, e.g.: print "@list[$i..$i+$n]"; changing the value of $n as required.