Replaceit is a quick, light and effective replacement to the combination of sed/awk/grep/head/tail and other such shell utilities, as well as being quicker in startup (at least) than an equivalent perl solution.

replaceit has various rules which can be used to enhance its abilities when negotiating tricky sections of text, whilst searching for the right one to replace, these include [ on same line ] string inclusion dependence, exclusion dependence, pre-existence, post-existence.

note: replaceit is a line-by-line file parser, so it cannot (at this point) process across multiple \n[\r] terminated lines.