my ($matrix, $limits) = @_;  # I get my data and limits from the arguments of subroutine
my $j = 1;
my ($pdl1, $pdl2, $n1, $n2);
my ($angle, $dotproduct, $d, %angles);
$pdl1 = pdl (@{$matrix}[0]);
$n1 = norm $pdl1;
while ($j<=$#{$matrix}) {
    $pdl2 = pdl (@{$matrix}[$j]);
    $n2 = norm $pdl2;
    $dotproduct = inner ($n1, $n2);
    $d = $dotproduct->sclr();
    $angle = (180/3.14159)*acos($d);
    $angles{$j} = $angle;
    $j++;
}
my @sorted = sort {$angles{$a} <=> $angles{$b}} keys %angles;