vim script for refactoring using a dictionary

refactor.vim

" Refactor the given lines using a dictionary
" replacing all occurences of each key in the dictionary with its value
function! Refactor(dict) range
  execute a:firstline . ',' . a:lastline .  's/\C\<\%(' . join(keys(a:dict),'\|'). '\)\>/\='.string(a:dict).'[submatch(0)]/ge'
endfunction

command! -range -nargs=1 Refactor :<line1>,<line2>call Refactor(<args>)

" Example of use
"  :%Refactor {'duck':'frog', 'frog':'rabbit', 'rabbit':'duck', 'I':'Noah'}
" changes 
"  I saw a duck, a frog, and a rabbit.
" to 
"  Noah saw a frog, a duck, and a duck.
"
" Note that the refactoring is not case independent, and only matches whole words.