1.      You can show count in clubs.  That is a common choice.  So you play first §3 and then §2.   It is then conceivable that South was 2-6-1-4 or 3-5-1-4 or even 2-5-2-4 in which case a third and fourth club will beat the contract if East has ©J.  Or partner might get it right and read you for four and switch to a spade.

2.      You can show attitude in clubs.  Your first card will be §2 and then you follow with §9.  A good partner should read this as you have no cause to play §9 if your original holding was §9 3 2 or §9 5 2 and declarer has false carded with §10.  With either of these combinations you will show your three card holding by playing your middle club next.

3.      If you play Roman signals[1] you have a choice.  You could play §2 and then §9 as before, giving the same message.  Or you could play §9 first and then §3 or §5 to discourage and indicate a spade switch.  In fact, by playing §9 first you  are unlikely to get partner to continue the suit as the only combinations where you will hold two are §9 2 and §10 9.

But whatever signals you play, try the hand out on your favourite partner to ensure you are in agreement.  Playing with a strange partner, I would recommend option 2.  If partner cashes two clubs and plays a bovine third you have done your best and he needs to rethink his analysis.

Of course the opponents overbid.  But bad defence is why they do it!.