function disableSubmit(form) {
  var elements = form.elements;
  for (var i = 0; i < elements.length; i++) {
    if (elements[i].type == 'submit') {
      elements[i].disabled = true;
    }
  }
}

<form method="get" onsubmit="disableSubmit(this)">
  <input type="text" name="q">
  <input type="submit" value="search">
</form>

### Google 画像検索へのリンクプラグイン
# usage: {{google_image('keyword')}}
sub google_image {
	my ($str) = @_;
	my $prefix = q(http://images.google.com/images?q=);
	my $enc = Jcode->new($str)->utf8;
	$enc =~ s/([^0-9a-z_ ])/'%'.unpack('H2', $1)/gei;
	$enc =~ s/\s/+/g;
	return qq(<a href="$prefix$enc" title="Google Images - $str">Google 画像検索 - $str</a>);
}