Why?

If I got that error then the first thing I would want to know is "against which version of perl was the object built ?" and my second question would be "which version of perl has loaded the object ?".
Armed with that information one is well on the way to knowing what has gone wrong, and how to avoid the problem in the future.

On windows (and I think on nix-type systems, too) the 2 perls don't need to be the exact same version (right down to the subversion number).
Sure, they both need to be the same revision and version numbers, but the subversion numbers should not need to match - the only requirement there being that the subversion number of the perl that built the object is less than or equal to the subversion numer of the perl that loaded the object.
It would be reassuring to see that this check is alert to that ... though I expect it is.

Seems a bit odd to me that perl croaks because 2 different versions of perl have got involved, but won't give you any useful information as to what those 2 version are.
In what way does providing the 2 handshake numbers help us ?

Cheers,
Rob