As black I respond to e4 with d6[edit].  I think I am playing the pirc?  Normally following with Nc6 and f6 on move 3.  What opening lines should I study to better my understanding of d6 as a response.  Am I correct that this can turn into a Sicilian, Caro or Pirc game.

Are you sure you typed that right?  1. e4 d6 is the Pirc.  I looked at some of your games and notice you often follow that up by moving a pawn to c6 and Nf6.  That heads into the Pribyl Defence or the Czech Pirc.  I don't know what transpositions are likely, but Cyrus Lakdawala's book 1...d6 Move by Move features the Pribyl and probably covers the transpositions.

Quasimorphy, yes I typed that wrong sorry for that.  1e4 ..d6 was my intended title.  What I meant by transpositions is what other systems are possible after d6.  I am comfortable with it and much difficulty switching my openings.  So I was wondering what systems would be practicle for me to study still using the d6 response to e4. Im finding that as go along with traditional book openings a single mistake can be fatal or win the game..  sometimes the error is just positionally bad but I'd like to broaden my ability and am trying to figure where to start 

e4 d6 is not a Caro. in the Caro you play c6 intending d5.

I just did some reading on the Caro, and came across the idea alot that that books "move by move" are the best as they address the theory for each move.  The Caro seems instinctive to me so I suppose that will be my next bit of fun.  

Seraphimity, here is a line from 1 e4 d6:

1 e4 d6 2 d4 Nf6 3 Nc3 Nbd7 4 Nf3 e5 is called the Lion.  The Lion can be reached from multiple move orders, such as the Philidor 1 e4 e5 2 Nf3 d6 3 d4 Nf6 4 Nc3 Nbd7.  Notice that the move ...Nbd7 helps avoid the exchange of queens.  Seraphimity, can this be a coincidence that you have a Lion in your avatar?

1.e4 e6 can lead to French Defence for Black if he intends to play 2...d5 on the next move. But Black can't cooperate and can play 2...c5 and lead to sicilian lines.

thanks for that, I actually move Nbd7 in most games as black.  I also have played the rat for fun, 1.d6 2.Nbd7 but mostly to through of a better opponent who is coming out with an off open..  I'll keep the "lion" handy and wait for a chance, Thanks!