# This subroutine returns true if its argument is tainted, false otherwise. 
sub tainted {
    local($@);
    eval { kill 0 * $_(0) };
    $@ =~ /^Insecure/;
}
1;

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I found the above code on the internet. It claims to do taint checking, but I'm not savvy enough to understand whats going on. I don't want to trust this subroutine to verify that my form data is safe if I don't know understand it.

As I understand the first bit, it somehow evaluates $_(0) to see if any processes start (and kills them). I think...and why does it only have to evaluate the first element of the array?

And I'm not sure under what circumstance $@ would match ^Insecure.
Thanks.

Edit: BazB added code tags.

Edit: ysth change title from: explanation please?

In reply to Please explain this tainting behaviour by Anonymous Monk

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