help please

[gargonx]

let's take the word "dogs"

   ext = dict("D":"V1",  "O":"M1", "G":"S1")
   std = dict("S":"H")

encode("DOGS") # proc()
we'll get: "V1M1S1H"

let's say i want to do just the opposite
word: "V1M1S1H"
decode("V1M1S1H")
    #how do i decode "V1" to "D", how do i keep the "V1" together?
and get: "DOGS"

#everything gets changed to uppercase