Vim Case-Agnostic Regex

I've run into the following case a few times and I was wondering if there is a fast way to handle it in Vim.

I'll have a source file like the following:

#ifndef _FOO_H_
#define _FOO_H_

class Foo {
    Foo(int foo);
};
#endif

And I would like to convert it to the following:

#ifndef _BAR_H_
#define _BAR_H_

class Bar {
    Bar(int bar);
};
#endif

So, I want all foo -> bar, but to keep the capitalization of the original. Right now, I've been doing this with 3 or 4 different regexes, but it seems there should be a better way. Any ideas?

From stackoverflow

• This script will do a case-preserving search/replace.

  Copy the script to the plugin directory (~/.vim/plugin), then do

  :set ic
  :%s/foo/\=KeepCaseSameLen(submatch(0), 'bar')/g
  

  Luc Hermitte : You should update your version of keepcase. I've added a :SubstituteCase command to it that simplifies substitutions a lot. :)

• Use emacs? (/runs)

  Arkadiy : :) not running fast enough.