If I wrote something in plperlu, and it used a Perl module (e.g. MyModule::Foo), when would that module be reloaded? Does it keep track of them like mod_perl's Apache2::Reload, so that a touch will cause a reinterpretation?
After some testing based on what Leon commented, apparently MyModule::Foo stays in memory from the first time it gets used successfully, but only within the current process (i.e., database handle.)
If there were errors in either compiling it (it would complain when you defined a function that use'd it) or using it (when you select from your function, for example), it'll reload it. However, I can't see a way to force it to reload within a process once it successfully runs, even by calling a different sub in the module that does error out.
Also, if you're accessing PostgreSQL via Apache::DBI, this means your cached handles won't pick up module changes unless you disconnect all the cached handles.
So I guess there's no way to force a check within a process, a la Apache2::Reload...