As a programmer I'm surprised you don't know the reason for a "1" showing at the bottom of your page.

I would guess the reason for two pages displaying is that you have:

GT::Plugins->action(STOP);

....in the wrong place (i.e. AFTER you have already returned instead of before, so it never gets called).

As for the "1", it's probably because you are printing a print.....

print GForum::Template->parse_print('error.html', { error => "FOO" } );

Try:

GForum::Template->parse_print('error.html', { error => "FOO" } );