There's a long-standing rule in Unix that one should never check the value of errno except immediately following a failed system call -- otherwise there are no guarantees about its value. Since $! is a magic alias for errno, the same rules apply. That's basically what perlvar says about it, too:

If used in a numeric context, yields the current value of errno, with all the usual caveats. (This means that you shouldn't depend on the value of $! to be anything in particular unless you've gotten a specific error return indicating a system error.)

In reply to Re: why would a successful eval of a require reset $!? by tall_man
in thread why would a successful eval of a require reset $!? by blahblahblah

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