I am almost certain that your problem in this scenario relates to user permissions - I would presume that all of your early testing of this script was carried out from the command-line, under your normal user account. This would mean that any tied-hash file store created would be owned by your user account with permissions as per your account umask.

Most web servers are configured to run as the user "nobody" with minimal permissions. As this user, my guess is that your script either cannot open the tied-hash file store previously created or cannot open the tied-hash file store in the user directory specified - For confirmation of this, I would examine the value of the $@ variable which will most likely provide an indication as the the reason why your script cannot open the tied-hash file store.

 

perl -e 'print+unpack("N",pack("B32","00000000000000000000000111000001")),"\n"'