# Count number of atoms
    
    if ($_ =~ /^ATOM/) {
        ++$count;
    }
}
close *ARGV; ## Add this.

##</code><code>##

@a = 1 .. 10;
$a[0] = 1;
$a[1] = 2;
$a[2] = 3;
...
$a[8] = 9;
$a[9] = 10;

##</code><code>##

# Calculate distance between all atom coordinates

foreach $i ( 0 .. $count-1 ) {

    foreach $j ( $i + 1 .. $count-1 ) {
    
    $dist = sqrt(
            ($arrayx[$i] - $arrayx[$j])**2 +
            ($arrayy[$i] - $arrayy[$j])**2 +
            ($arrayz[$i] - $arrayz[$j])**2
        );
    
    print "$dist\n";
    
    }
}