#!/bin/sh

process () {
	local old="$1"
	local new="${1//$first/$second}"
	[[ ! -e "$new" ]] && {
		mv "$old" "$new" || exit 1
	}
}

first="$1"
shift
second="$1"
shift
while [[ "$1" != "" ]] ; do
	process "$1"
	shift
done