How to write to the error log?
 

Or any log?

I'm having problems where a module isn't doing what I think it should, and as such, I need to start tracing the values of variables as it proceeds and see just where the error is happening.

To do this, I often just dump info to the screen but in a highly segmented application like this - that's not really possible. So adding commands that output various information to a log would be a natural choice to help me debug.

Is there a standard method to output to the log?