He wrote:

And I want to be able to write a perl script that will randomly select 3 of this files and print the contents of the remainder (i.e. the other 33 files) into one file like this

It seems to me that he wants an output file for each of the Binomial(36,3)=7140 choices of three files out of 36. I'm not sure where you get this 33! thing from. Maybe I overlooked something.