#!/usr/bin/perl
use strict;
use warnings;


my $passwd = '/etc/passwd';
my @users = ();

open my $in, '<', $passwd or die "$passwd: $!\n";

while ( my $line = <$in> ) {

	my ( $user ) = split( /:/, $line, 2 );
	
	push @users, $user;
}

close $in;

@users = sort @users;

print "@users\n";