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

sub NEXT { $_[0]->() }

sub string_to_char_iter {
	my $string = shift;
	$string = reverse $string;
	sub { '' ne $string ? chop $string : undef }
}

my $string = join '', 'a' .. 'z';
my $iter   = string_to_char_iter $string;

while ( defined ( my $char = NEXT $iter ) ) {
	print "$char\n";
}