use WWW::Mechanize;
   my $mech = WWW::Mechanize->new();
$mech->get("$mydomain/post.php");

$mech->form_number(2);
$mech->field("headline","MyHeadline"); 
$mech->field("thecontent","MyContent"); 
$mech->field("categories[some_tag]","Blah"); 
$mech->click("publish");