Ouch. Please. @foo[0] hurts my eyes. Surely you meant to say:

$_[0] = $arg1,
$_[1] = $arg2,
$_[2] = $arg3,
$_[3] = $arg4,
$_[4] = $data[0],
$_[5] = $data[1]
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A single-element slice is almost never what people want. Warnings-on would have told you that.

-- Randal L. Schwartz, Perl hacker