If you want to loop through two arrays at the same time without modifying them, you could use something like:

#!/usr/bin/perl -wT
use strict;

my @a = (1,2,3,4,5,6,7);             # make a couple of arrays
my @b = reverse @a;

my $maxlen = $#a > $#b ? $#a : $#b;  # find the last index of the larg
+est one

for my $index (0..$maxlen) {         # loop through the indexes
  my $aval = $a[$index];
  my $bval = $b[$index];

  print "\$a[$index]=$aval  \$b[$index]=$bval\n";
}

=OUTPUT
$a[0]=1  $b[0]=7
$a[1]=2  $b[1]=6
$a[2]=3  $b[2]=5
$a[3]=4  $b[3]=4
$a[4]=5  $b[4]=3
$a[5]=6  $b[5]=2
$a[6]=7  $b[6]=1
[download]

-Blake