Multiple string.replace()

I'm trying to search and replace words in a long string in FIOC.


(pseudocode)
for i between 0 and 10:
  str = str.replace(words[i], replacements[i])

However, since strings are immutable, the string is copied each time and is slow. Since the length of the words are exactly the same as the replacements, I would like to edit the original string directly. Is that possible somehow?

>>4
One thing I should say is that
When I want to replace "aaa" with "bbb", I need it to work with "aaa123aaa" -> "bbb123bbb" as well. I don't think this code will do this at the moment.