Theta

#!/usr/bin/perl
use strict;
use warnings;
use feature 'say';
use Math::Trig;
my $cos = {};
my $sin = {};
sub theta {
  my ($x1, $y1, $x2, $y2) = map { deg2rad int $_ } @_;
  $cos->{$x1} or $cos->{$x1} = cos $x1;
  $sin->{$x1} or $sin->{$x1} = sin $x1;
  $cos->{$y1} or $cos->{$y1} = cos $y1;
  $sin->{$y1} or $sin->{$y1} = sin $y1;
  $cos->{$x2} or $cos->{$x2} = cos $x2;
  $sin->{$x2} or $sin->{$x2} = sin $x2;
  $cos->{$y2} or $cos->{$y2} = cos $y2;
  $sin->{$y2} or $sin->{$y2} = sin $y2;
  my $theta = rad2deg(
    acos(
      (1 - (1 / 2) *
        (
          ($cos->{$y1} * $sin->{$x1} - $cos->{$y2} * $sin->{$x2}) ** 2 +
          ($cos->{$y1} * $cos->{$x1} - $cos->{$y2} * $cos->{$x2}) ** 2 +
          ($sin->{$y1} - $sin->{$y2}) ** 2
        )
      )
    )
  );
  return $theta;
}
my $data = [];
while (<>) {
  chomp;
  next if /\A\s*\z/;
  my @d = split;
  next if 2 != (scalar @d);
  push @$data, \@d;
}
my $size = scalar @$data;
for (my $i = 0; $i < $size; $i++) {
  for (my $j = $i + 1; $j < $size; $j++) {
    my $r = [$data->[$i][0], $data->[$i][1], $data->[$j][0], $data->[$j][1]];
    push @$r, theta @$r;
    say join "\t", @$r;
  }
}