use strict;
use warnings;
 
my $ncol;
while (<DATA>){
  my ($id,@acgt)=split;
  my (%count,@reports);
 
  # -- count ACGT
  $count{$_}++ for (@acgt) ;
 
  # -- print in descending order
  while( my ($marker,$number) = each %count ) {
    push @reports, "$number $marker";
  }
  print "Column :",$ncol++,"\n";
  no warnings "numeric";
  print join ("\t",sort {$b <=>$a} @reports),"\n";
}
 
__DATA__
3851 A A G G T T A A C C
3854 A A G G T T A A C C
3871 A A G G T T A A G G

##</code><code>##

Column :0
4 A	2 T	2 C	2 G
Column :1
4 A	2 T	2 C	2 G
Column :2
4 A	4 G	2 T