It really depends. On perl5.6.x (and probably earlier), this will cause Attempt to free unreferenced scalar at - line 2. 
    @a = (bless {}, 'X');
    sub X::DESTROY { @a = () }
    @a=();
__END__

[download]
Whats important to note is that the warning comes with a line number, which you can use to investigate (it should give away which variable caused it). If XS is to blame, it should be possible check wether SvREFCNT_dec() was called too many times, or that SvREFCNT_inc() was called too few times, or that the SV was mortalized when it shouldn't have been, or that memory has been corrupted.

MJD says "you can't just make shit up and expect the computer to know what you mean, retardo!"
I run a Win32 PPM repository for perl 5.6.x and 5.8.x -- I take requests (README).
** The third rule of perl club is a statement of fact: pod is sexy.

In reply to Re: Mark-and-sweep-like mechanism to verify refcount integrity by PodMaster
in thread Mark-and-sweep-like mechanism to verify refcount integrity by nobull

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