I see. You need to replace all:
Code
print(qq~Status: HTTP/1.1 301 Moved Permanently\n~ );
Code
print(qq~Status: HTTP/1.1 302 Moved Temporarily\n~ );

with:
Code
print(qq~Status: 301 Moved Permanently\n~ );
Code
print(qq~Status: 302 Moved Temporarily\n~ );

The redirection URLs are also outdated. You need to replace:
Code
print(qq~Location: $URL/ubbthreads.php/ubb/showflat/Forum/$in{'f'}/topic/$in{'t'}/Number/$in{'p'}/site_id/$site_id#import\n\n~);
with something like:
Code
print(qq~Location: $URL/ubbthreads.php/topics/$in{'t'}/\n\n~);