So gnulib-tool is a 4500 line shell script which you would like to re-implement to ease maintenance, with the side benefit of possibly being a bit faster? If performance was the main reason it would probably be quicker to hack on bash a bit to speed it up.
If you really want to re-implement it, then for the problem domain I would suggest a scripting language. You mention python has backwards compatability issues. I wrote a large enough python program against V1.52, which only needed 1 trivial tweak to be compatible with 2.x That's 8 years or so now of compatability. I've just started with perl myself (and compared to python I hate it :)), but given that the autoconf etc. are written in perl I would think it's the best choice? cheers, Pádraig.
