In Perl, how can I generate all possible combinations of a list?

Question

I have a file with a list, and a need to make a file that compares each line to the other. for example, my file has this:

AAA  
BBB  
CCC  
DDD  
EEE

I w

Answer 1

Take a look at Math::Combinatorics - Perform combinations and permutations on lists

example copying from the CPAN:

use Math::Combinatorics;

  my @n = qw(a b c);
  my $combinat = Math::Combinatorics->new(count => 2,
                                          data => [@n],
                                         );

  print "combinations of 2 from: ".join(" ",@n)."\n";
  print "------------------------".("--" x scalar(@n))."\n";
  while(my @combo = $combinat->next_combination){
    print join(' ', @combo)."\n";
  }

  print "\n";

  print "permutations of 3 from: ".join(" ",@n)."\n";
  print "------------------------".("--" x scalar(@n))."\n";
  while(my @permu = $combinat->next_permutation){
    print join(' ', @permu)."\n";
  }

  output:
combinations of 2 from: a b c
  ------------------------------
  a b
  a c
  b c

  permutations of 3 from: a b c
  ------------------------------
  a b c
  a c b
  b a c
  b c a
  c a b
  c b a