Filtering to documents containing two fields with the same value?

I've got data that has had two different language recognition algorithms run on it. I would like to build a filter such that if langRec1==langRec2, I get the record back. I could exhaustively set up a list of all the language codes, but I wanted to check if there was a more intelligent way of going about this.
Essentially, I want to be able to filter documents based on two fields containing exactly the same value. I might not know what the values are, but I want to be exhaustive. Is this possible?