barney@spadge:/media/Music$ old="hello%20my%20friend"
barney@spadge:/media/Music$ new=${old//%20/ }
barney@spadge:/media/Music$ echo "$new"
hello%20my%20friend
barney@spadge:/media/Music$ new=${old//ie/ }
barney@spadge:/media/Music$ echo "$new"
hello%20my%20fr nd