Given the fact that the entire call/uncall mechanism is based on keeping the original parameters that are required to undo the calculation - it will work fine,

Given the fact that the entire call/uncall mechanism is based on keeping the original parameters that are required to undo the calculation - it will work fine, but you won't be able to call the undo on the result you got from any other source (i.e. not through the call/uncall mechanism) read the source for p-divmod (one of the most useful functions in cryptography). You need to pass the original y to get back the original x in the reverse