Not sure what you want, you seem to mean the "loop variable" and not an "iterator"¹.

Anyway like always there is a way to do it in Perl!

(... but "easy" isn't necessarily the first attribute which comes to mind here... neither is "recommendable"² ;-)

The following code tries to cover all thinkable use cases:

my @a="a".."c";
my @b=1..3;

print "@a\n";

our $alias;
*alias=\$a[2];
{
  local $a[1]; # otherwise $a[1] is undefined after the loop
  while ( $a[1] = <@b>) {
    $alias=$a[1]+1;
    print "@a\n";
  }
}

print "@a\n";
__END__
a b c
a 1 2
a 2 3
a 3 4
a b 4
[download]

¹) from perlglossary

      iterator
           A special programming gizmo that keeps track of where you a
+re in
           something that you’re trying to iterate over.  The "foreach
+" loop
           in Perl contains an iterator; so does a hash, allowing you 
+to each
           through it.
[download]

²) NB the elements of @b are stringified in the loop...