if ($#_ <= 255) {
    my $lim = $#_;
    &$sub(($_[0][0],$_[1][0],$_[2][0],$_[3][0],$_[4][0],
           $_[5][0],$_[6][0],$_[7][0],$_[8][0],$_[9][0],
           ...
           $_[255]
          )[0..$lim]);
    $#_ = $lim # remove autovivified arrayrefs
} else {
    eval "&\$sub( " . join( ", ", map "\$_[$_][0]", 0..$#_ ) . " )";
}