If its an automated redirect between the pages (which is quite common) with, which mechanize cannot cope, add this to your code:

after this :

$mech->follow_link(n=>4 ); #4 is your link number
or
$mech->submit();# or form submit

add this (to follow the redirection correctly):

$mech->follow_link(n=>0);



you can try accessing the root of the page and then following the link.