Gohla

#! /usr/bin/osascript

on replace_string(input, search, replacement)
	set oldDelim to AppleScript's text item delimiters
	set AppleScript's text item delimiters to search
	set textItems to every text item of input
	set AppleScript's text item delimiters to replacement
	set res to textItems as string
	set AppleScript's text item delimiters to oldDelim