# New Ticket Created by Zefram # Please include the string: [perl #132033] # in the subject line of all future correspondence about this issue. # <URL: https://rt.perl.org/Ticket/Display.html?id=132033 >
Since commit 167a0edf, Set.WHICH now hashes the concatenated .WHICHes of the set's elements, producing a fixed-size output. This inevitably means that some sets that would otherwise have had distinct .WHICH values will now clash. I can't give an example, because doing so would require constructing a SHA-1 clash, but it is inevitable that clashes will occur by this route. Since === on Sets follows .WHICH, it will perceive Sets to be identical based on hash coincidences. The hashing means that === can only perceive 2**160 distinct Set identities. This is distinct from the problem of Set.WHICH clashes arising from distinct sets of element .WHICHes concatenating to the same string, previously reported as [perl #128943]. -zefram
