sub rndPart1{ ## can overlap
    my( $start, $end, $count ) = @_;
    my $step = ( $end - $start ) / $count;
    $start += $step / 2;
    map{
        my $mid = $start + $step*$_;
        my $v = $mid + (
            ( $_ == 0 || $_ == ( $count - 1 ) )
            ?  ( rand( $step ) - $step/2 )
            :  ( rand( $step * 2 ) - $step )
        );
        sprintf "%5.2f", $v;
    } 0 .. $count-1;
}