I don't know the answer, but I just discovered that in Perl 1, the result of the == operator was 0 for false and 1 for true, instead of ""/1 as it is now. So there must have been a conscious decision to change it somewhere along the way. Why, I do not know. I will post more information is I find out anything else.

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Update: The change occurred in Perl 5.000. But it doesn't even appear to be documented. (If someone does find that it is documented, please let me know.)

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Tye just pointed out that the "" value is special. Normally, "" raises a warning if you convert it to a number. But the "" that results from a comparison does not:

    #!/bin/perl -w
    $x1 = "" + 0;
    $x2 = (1 == 0) + 0;
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This generates an "isn't numeric" warning for line 2 but not line 3.