Can you remember when it was added? Was it during your reign, or later than that?

The automatic implied defined() was added after my time as pumpking. When I discovered the danger of while (<>) {}, I didn't feel I could change the language without breaking things, so I added a warning instead. That warning was unsatisfactory to a lot of people, so the issue came up again, this time during one of Larry's more available periods. Somebody proposed the language change we have today, Larry OK'd it, and the patch was installed almost immediately.

    -- Chip Salzenberg, Free-Floating Agent of Chaos

Interestingly, your warning is still in effect. The only way I can throw it is through this bug:

# OK, gets implied defined(), no warning, correct output
% perl -lwe 'print while glob("{dog,cat,0,pig,cow}")'

  dog
  cat
  0
  pig
  cow


# Buggy, no implied defined(), throws warning and misbehaves
% perl -lwe 'print while $_ = glob("{dog,cat,0,pig,cow}")'

  Value of glob construct can be "0"; test with defined() at -e line 1
+.
  dog
  cat
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-Blake