while ($new_sock = $sock->accept())
{
...
while (defined ($buf = <$new_sock>))
{
  if ($buf =~ /^VERIFY:/)
  {
    if (verify_pass($buf))
    {
      print $new_sock "VERIFIED\n";
    }
    else
    {
      print $new_sock "NOT VERIFIED\n";
    }
  ...
...
}

sub verify_pass
{
  ($args) = @_;
  ($cmd, $user, $pass) = split(/:/, $args);
  chomp($pass);

  my $uid = getpwnam $user;
  my $pwd = (getpwuid $uid)[1];
  my $salt = substr $pwd, 0;
  my $enc = crypt($pass, $salt);

  if ($enc eq $pwd)    # Meaning success
  {
    return 1;
  }
  else
  {
    return 0;
  }
}