This is a useful link, but in my case it is inaccurate, or rather, incomplete.

In my particular environment, I also need to set the DB2INSTANCE environment variable to the name of the DB2 instance that I'm currently using. Failing to do that provokes the following error:

ERROR=Total Environment allocation failure!  \
Did you set up your DB2 client environment?
[download]

Apparently this is a known feature of using DB2 from Perl, and I've been told that the same things happens using Oracle.