another, well-known breach of this generalization — you can't use references as hash keys

This is a different issue. Hash keys are not scalar values, they are string values. It happens that, very often, the stringified value is the same as the useful scalar value. In some cases, though, this is not true. References are one example, but another would be a variable with a dual value. Consider the following example:

    open "non_existent_file";
    print $!+0, ": ", $!;
    $hash{$!}++;
    for (keys %hash) {
      print $_+0, ": ", $_;
    }

[download]

Which outputs the following:

    2: No such file or directory
    0: No such file or directory

[download]

The separate numerical value is lost, because the value is stringified as the hash key, not stored as an arbitrary scalar.

In reply to Re^7: ref eq "REF" by revdiablo
in thread ref == "REF" by gaal

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