  The problem 2-Xor-Sat asks for the probability that a random expression,
built as a conjunction of clauses $x \oplus y$, is satisfiable. We revisit this
classical problem by giving an alternative, explicit expression of this
probability. We then consider a refinement of it, namely the probability that a
random expression computes a specific Boolean function. The answers to both
problems involve a description of 2-Xor expressions as multigraphs and use
classical methods of analytic combinatorics by expressing probabilities through
coefficients of generating functions.
