#!perl -w
use strict;

sub print_in_columns {
  my %s;

  # Push the input array into the hash  to indicate which
  # columns are present
  @s{@_} = ();

  # Loop through the permitted values and either print
  # the value ( if it exists in the hash %s, or print 
  # an empty column if it isn't
  print exists $s{$_} ? "$_\t" : "\t" for ('A'..'G');
  print "\n";	
}

print_in_columns split // while <DATA>;

__DATA__
ABC
ADE
AFG
CDB