use URI;
my $uri = URI->new("http://www.foo.com/bar");
$uri->query_form( param_one => "hello+world&foo=bar",
  param_two => "blah" );
print "$uri\n";
# prints "http://www.foo.com/bar?param_one=hello%2Bworld%26foo%3Dbar&param_two=blah"