$a= 20;
$b= 22.5;
$c= 23
$atob = abs($a - $b) > 1 ? 1 : 0;
$btoc = abs($b - $c) > 1 ? 1 : 0;
$atoc = abs($a - $c) > 1 ? 1 : 0;

if ( $atob && $atoc && $btoc ) {
print OUTFILE "DIFF > 1 all three\n";
    $matrixflags[$row - 4][$i] = 1;
    $matrixflags[$row - 3][$i] = 1;
    $matrixflags[$row - 2][$i] = 1;
}
...