#! /usr/bin/perl

use warnings;
use strict;

$_ = 'abcdefghi';

# s/./ substr $_, -$+[0], 1 /eg;    # duh, substr and array
# s#.# /(.).{$-[0]}$/; $1 #eg;      # duh, array

my $x = 0; s#.# /(.).{$x}$/; $x++; $1 #eg;

print "$_\n";