"The power of structural regexps combined with proper Undo/Redo is also great - rather than pipe something through sed or awk, I'll often iteratively build up an expression or set of expressions that perform some particular one-off transformation, rewinding and retrying as necessary."
Thanks for this - it has just worked as a good start point for me. As a grumpy person who doesn't like searching for libraries, these "low barrier to entry" and "meta-library" ideas make me less grumpy.