Let's say I have a three lists of strings: 
my @sets = (
  [qw( a c f g e h i )],      # X
  [qw( a b c d e f g h i )],  # Y
  [qw( a c d e f g h i )],    # Z
);

[download]
What I'd like to accomplish is to display these side-by-side, probably in the following manner: 
X  Y  Z
a  a  a
   b
c  c  c
   d  d
   e  e
f  f  f
g  g  g
e     
h  h  h
i  i  i

[download]
To do this, I need to reconcile the discrepancies between the lists and come up with an array of arrays holding the indexes. In this example, the index array would be: 
my @idx = (
  [0, undef, 1, undef, undef, 2, 3, 4, 5, 6],  # X
  [0, 1, 2, 3, 4, 5, 6, undef, 7, 8],          # Y
  [0, undef, 1, 2, 3, 4, 5, undef, 6, 7],      # Z
);

[download]
I've chosen the order because sets Y and Z have the ordering of (d, e, f, g) in common, and set X is the odd one with (f, g, e).

So my question is, is this a job for a diff-like module, or some CVS-merge-like module, or what? The idea is to show the lists (which are very similar but probably differ in a couple places here and there) side-by-side and match them up as much as possible without altering their order. Or, put another way, I want to insert "null" elements into the lists as necessary to get them to line up such as I have them displayed.

Update: another problem I might run into is each set having a unique element: 

my @sets = (
  [qw( a b c f g )],  # X
  [qw( a b d f g )],  # Y
  [qw( a b e f g )],  # Z
);

[download]
resulting in: 
X  Y  Z
a  a  a
b  b  b
c      
   d   
      e
f  f  f
g  g  g

[download]
Jeff japhy Pinyan, P.L., P.M., P.O.D, X.S.: Perl, regex, and perl hacker
How can we ever be the sold short or the cheated, we who for every service have long ago been overpaid? ~~ Meister Eckhart

In reply to Reconciling multiple lists (similar to "merge" in CVS?) by japhy

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