Cookies and Perl

I have a client who is using and old (outdated and unsupported) php/perl CMS as an intranet site. In implementing a DRP (Disaster Recovery Plan) they switched all the server references in the code and on the server from the server IP address to a DNS name. This was done using a search and replace :-(
This effectively broke the intranet site. They were able to get most of it back up and running with the exception of logins and how sessions were managed. For some reason, once this CMS saw a domain name instead of an IP address, it changed the path in the cookie to something like this:
mywebserver/http://mywebserver/somesite
from what worked before which was:
mywebserver/somesite
We searched through config files and didn't find anything conclusive to begin with. Then we found some code where cookies were being created and modified it so that after the cookie string was created we did some string manipulation on it like this:
$setcookie =~ s/http:\/\/mywebserver//m
This resets the setcookie var by searching through the setcookie var (it's a multiple line string so we needed to use /m) for the string 'http://mywebserver', replacing it with nothing.
It turned out that the CMS was creating more than one cookie, so we found this bit of code in two more files, added our hack there, and sessions worked again!
I have to confess, I was surprised that this little hack worked.