> you can then read in stuff with something like input.split("\t").map(unescape)

What about input lines like 'asdf\\thjkl\tzxcvb'? That should be two fields, one the string ‘asdf\thjkl’ and the other the string ‘zxcvb.’

I think that your way is a bit like trying to match context-free grammars with a regular expression. The right way is to parse the input character by character.