I am attempting to write a code that finds all overlapping images from a list of images and their maximum and minimum latitudes and longitudes.

The Input file looks like this:

"Image number","minlat","maxlat","minlon","maxlon"

1,0,30,20,50

2,10,30,70,90

3,70,80,40,50

4,40,70,20,50

Here is the code, which is likely inefficient and riddled with errors, (this is my first programming language). Right now I'm just trying to compare the minimum latitudes. I've removed some warnings and comments

 #Permutation loop

my @n;
my $n = 1;
my %Image_info;

## Sort the data into a new hash.

while (<>)  {
    split /,/;
        $Image_info{$_[0]} = {
            latmin => $_[1],        
            latmax => $_[2],
            lonmin => $_[3],
            lonmax => $_[4],
        };
};

## Redifine the hash elements as scalars and begin comparison loop.

for (keys %Image_info) { 
    my $latmin1 = $Image_info{$_} -> {latmin};
    my $latmax1 = $Image_info{$_} -> {latmax};
    while ($n < 11)  {
        my $latmin2 = $Image_info{$n} -> {latmin};
        my $latmax2 = $Image_info{$n} -> {latmax};       
        if ($latmin1 > $latmin2) {
            print $latmin2, " is less than ", $latmin1, ".\n";
        };
    $n = $n +1;
    };
}

[download]

This is the output:

Use of implicit split to @_ is deprecated at overlap.plx line 19.

0 is less than 70.

10 is less than 70.

40 is less than 70.

The output is close but it should also print 0 is less than 10 and 10 is less than 40 ect. Can anyone tell me how to code this more effectively? Thanks in advance.

In reply to Permutation and comparison loop by spacegeologist

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