s/            # search for...
 \(            # a literal "("
 (             # begin storing what follows (in "$1")
 [^)]*         # zero or more of anything that is *NOT* ")"
 )             # stop storing in "$1"
 ;             # a semicolon
 (             # begin storing what follows (in "$2")
 [^)]*         # zero or more of anything that is *NOT* ")"
 )             # stop storing in "$2"
 \)              # a literal ")"
 /($1,$2)/gx;        # and replace all that with...see below...