Have you done any research on what that error code means? If it's coming from the webserver, check the webserver's documentation.
Off the top of my head, though, the following strikes me as most likely: if the server's OS has changed, then there are two things that could have gone wrong: either Perl is not installed on the new OS, or your webserver does not "know" that .pl files are to be run through the Perl interpreter. Make sure that .pl is associated with the perl.exe file on the server.
If not P, what? Q maybe?