Can anyone see a time when this would fail?

It would be entirely possible for a future version of perl to numify a reference to something other than an actual memory address, or to have SVs that are less than 12 bytes apart. (I don't know offhand whether Ponie is already planning to break either of those assumptions.)

For existing v5.x perl I'm not aware of any situation in which your assumptions would be invalid.

Hugo

In reply to Re: Circular reference testing. by hv
in thread Circular reference testing. by BrowserUk

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