#!/usr/bin/perl -l
use strict;
use warnings;
use Encode qw/_utf8_on/;
for my $str (split /:/, shift||'a:bc') {
    _utf8_on($str);
    print "$str\t", substr(lc($str), 0);
#   use Devel::Peek; Dump substr(lc($str),0);
}

##</code><code>##

x x
yz yz

##</code><code>##

x x
yz y