I come to ya'll once again for a little help with tweaking my code. I was working on making a routine to make the list of vertex that I have, run clockwise if they are not listed that way already. My algorithm is pretty simple: 1) find the largest y-value, 2) compare the next vertex's x-value to that of the largest y-value, 3) roughly, if the difference is positive, then it is clockwise, otherwise reverse the order. Now my code works for most cases, yet it does wrong on a case like: 
|      ^
|    / /
|   /  |
|   ---
---------

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the list comes in going clockwise, but my algorithm changes it because the next x-value after the greatest y-value is less than the x-value of the greatest y-value. Any help would be much appreciated. Thanks 
my ($highest, $hv, $xclock, $negx);
my @backwards;
# MAKE CLOCKWISE *************************************
CLK: for $i (0..$#blocks) {
    $highest = 0;
    for $j (0..$#{$blocks[$i]}) {
        if ($blocks[$i][$j][2] > $highest) {
            $highest = $blocks[$i][$j][2];
            $hv = $j;
        }
    }
    if ($hv == 0) {
        print "zero [$i][$i][$i][$i][$i]\n";
        $xclock = $blocks[$i][($hv + 1)][1] - $blocks[$i][$hv][1];
        if ($xclock == 0) {
            $xclock = $blocks[$i][($hv + 2)][1] - $blocks[$i][$hv][1];
            }
        $negx = $blocks[$i][$hv][1] - $blocks[$i][($#{$blocks[$i]} - 1
+)][1];
        print "00000 blk [$i][$hv] clkwise [$xclock], [$negx]\n";
        if ($xclock == 0) {
            print "xclock 0 \n";
            if ($negx < 0) {
                print "change xclock 000\n";
                @backwards = reverse @{$blocks[$i]};
                for $k (0..$#backwards) {
                    print "xcl0000 [$k][1] $backwards[$k][1]\n";
                    print "xcl0000 [$k][2] $backwards[$k][2]\n";
                }
                @{$blocks[$i]} = @backwards;
                next CLK;
            }
        }
        if (($xclock < 0) ) {
            print "change 000\n";
            @backwards = reverse @{$blocks[$i]};
            for $k (0..$#backwards) {
                print "0000 [$k][1] $backwards[$k][1]\n";
                print "0000 [$k][2] $backwards[$k][2]\n";
            }
            @{$blocks[$i]} = @backwards;
            next CLK;
        }
    }
        
    $xclock = $blocks[$i][($hv + 1)][1] - $blocks[$i][$hv][1];
    if ($xclock == 0) {
        $xclock = $blocks[$i][($hv + 2)][1] - $blocks[$i][$hv][1];
        }
    $negx = $blocks[$i][$hv][1] - $blocks[$i][($hv - 1)][1];
    print "BBBBBBBBBB [$i][$i][$i]\n";
    print "blk [$i][$hv] clkwise [$xclock], [$negx]\n";
    if (($xclock < 0) || ($negx < 0)) {
        print "change reg\n";
        @backwards = reverse @{$blocks[$i]};
        for $k (0..$#backwards) {
            print "[$k][1] $backwards[$k][1]\n";
            print "[$k][2] $backwards[$k][2]\n";
        }
        @{$blocks[$i]} = @backwards;
        next CLK;
    }
}

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In reply to Making CLOCKWISE work by stu96art

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