The ops used for looking up an array in scalar context are different for pad vars and for global vars (pp_padav vs pp_rv2av). One of those ops was optimised by me such that, when returning a zero value, it returned the special SV PL_sv_zero rather than setting a PADTMP SV to zero and then returning that. I don't remember offhand why the other op wasn't or couldn't be similarly optimised. Apart from esoteric uses (such as inspecting the internals with Peek()), the two different return values should generally have the same behaviour. Both evaluate to 0 in numeric context and to "0" in string context. Just with different overheads. Serializers tend to struggle with such things, but that's a general problem with perl's polymorphic internal representations of values. For example, for a hypothetical serializer function, you typically get this behaviour: 
    my $x = 0;
    serialize($x); # outputs an integer
    say "x=$x";    # $x now has both valid int and string representati
+ons
    serialize($x); # outputs a string

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Dave.

In reply to Re^2: Reason for this discrepancy with scalar? by dave_the_m
in thread Reason for this discrepancy with scalar? by kikuchiyo

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