Here is a little Ruby library that may be useful to you. It is a regular expression string replacing tool. It’s similar to what you can do with String#gsub in Ruby, but with a few more features.

I needed this library to get Textmate snippets working in Redcar, and therefore it uses a slightly different syntax to gsub (“$1” instead of “\1”). Here are some examples:

rr = RegexReplace.new(/nuclear (\w+)/, "solar $1")
  rr.rep("nuclear nutcracker")
  => "solar nutcracker"

So far so obvious. That’s identical to Ruby gsub but with “\1” changed to “$1”. Here’s something more useful:

rr = RegexReplace.new(/nuclear (\w+)/, "solar \\u$1")
  rr.rep("nuclear nutcracker")
  => "solar Nutcracker"

Whee! Letters following “\u” are upcased. What else can it do?

Upcase stretches with \U…\E

rr = RegexReplace.new(/nuclear (\w+)/, "solar \\U$1\\E")
  rr.rep("nuclear nutcracker")
  => "solar NUTCRACKER"

You can downcase in exactly the same way with “\l” and “\L..\E”.

Conditional replacement with (?1:then:else)

rr = RegexReplace.new(/nuclear( \w+)?/, "solar(?1:$1: thingy)")
  rr.rep("nuclear nutcracker")
  => "solar nutcracker"
  
  rr.rep("nuclear")
  => "solar thingy"

You can also combine the operators in this fashion “\l\U…\E” to get (for instance) “fOO” from “foo”.

If you find it useful please let me know.