sub probe {
    use integer;
    my( $aref, $lo, $hi, $limit, $istep ) = @_;
    my $step = ( $hi - $lo ) / $istep;
    {
        my $i = $lo;
        $i += $step while $i <= $hi and $aref->[ $i ] <= $limit;
        if( $i >= $hi ) {
            if( $aref->[ $hi ] == $limit ) {
                --$hi while $aref->[ $hi - 1 ] == $limit;
                return $hi;
            }
            $step /= 2;
        }
        else {
            $limit = $aref->[ $i ];
            $lo = $hi - $step; ## Update: Swapped the order of this line and the next
            $hi = $i;
            $step = int( ( $hi - $lo ) / $istep ); # $istep was wrongly '10'
        }
        redo;
    }
}