Large chunks of code should be preloaded in libraries. Code in BML pages is re-evaled on every request, so it should be small. If you need a lot of code, put it in a library and load it in cgi-bin/lj-bml-(init|local).pl Don't write temporary files to disk... all LJ code should be able to run on a cluster of web servers with no disk-based session persistence. If you're calling a function with a $dbarg parameter and you have both a $dbs and $dbh available, call the function with your $dbs ... otherwise the function and all its callees can't ever use the slave databases.