It is possible to test a material for chlorine by heating up a piece of solid copper wire (without insulation) with a torch and sticking it into the material you want to test so you get a bit of the material melted onto the copper wire. Then you put it back into the torch flame and if there is a green flame (in the first second or so) then that is an indicator of chlorine.
Disclaimer: A friend told me about this method. I haven’t tried it myself and I don’t know if it’s solid science.