One can also mention these forums
Try, if not posting, solving the problems which occur here.
This will mostly improve your awk/sed/regex understanding, cause nothing beats practice.
Then compare your code to the one who responded before you.
It will probably be much shorter and more efficient (in the start).
Learn from it and try to 'disassemble it'.
A great part of these forums is text parsing and requests to convert data, matching strings, lines before and after and other more or less mundane tasks.