VCS::Lite - Minimal version control system


  use VCS::Lite;

  # diff

  my $lit = VCS::Lite->new('/home/me/foo1.txt');
  my $lit2 = VCS::Lite->new('/home/me/foo2.txt');
  my $difftxt = $lit->delta($lit2)->diff;
  print OUTFILE $difftxt;

  # patch

  my $delt = VCS::Lite::Delta->new('/home/me/patch.diff');
  my $lit3 = $lit->patch($delt);
  print OUTFILE $lit3->text;

  # merge

  my $lit4 = $lit->merge($lit->delta($lit2),$lit->delta($lit3));
  print OUTFILE $lit4->text;


This module provides the functions normally associated with a version control system, but without needing or implementing a version control system. Applications include wikis, document management systems and configuration management.

It makes use of the module Algorithm::Diff. It provides the facility for basic diffing, patching and merging.



The underlying storage concept of VCS::Lite is an array. The members of the array can be anything that a scalar can represent (including references to structures and objects). The default is for the object to hold an array of scalars as strings corresponding to lines of text.

The basic form of the constructor is as follows:

  my $lite = VCS::Lite->new( '/my/file');

which slurps the file to make an object. The full form is as follows:

  my $lite = VCS::Lite->new( $object_id, $separation, $source, ...);

This is a string to identify what is being diffed, patched or merged, in the application's environment. If there is no $source, this is used as a filename from which to read the content.


This is an optional parameter, which can be used via $/ to split the input file into tokens. The default is for lines of text. If you pass in a string to be tokenized, this will use $sep as a regular expression

$separation can be a scalar or scalar ref, where this is used to break up the input stream. All values permitted for $/ are allowed (see perlvar).

$separation can also be a hashref, to give a finer level of control. For example:

  {  in => '\n',
     out => '\n',
     chomp => 1 }

'in' is the input record separator to use (the same as you would pass as $sep). Note that all values allowed for $/, and indeed the value of $/ passed in is what is used as a default. 'in' can be a string or a regexp.

'out' is the character used on joining the members to output the results (text method in scalar context). This is the output record separator $\. Note that 'out' defaults differently depening on the setting of 'chomp': if 'chomp' is off, 'out' will default to the empty string, or rather the passed in value of $\. If 'chomp' is on, 'out' will default to 'in' - note that you should specify 'out' explicitly if you are using a regexp for 'in'.

If the 'chomp' flag is set, the text matching 'in' is removed from the input lines as they are read. 'chomp' is not on by default, as this is new functionality in release 0.08.


if unspecified causes $object_id to be opened as a file and its entire contents read in. The alternative is to supply $source, which can be one of the following:


This is a string which is tokenized using $separation


Array of tokens

filehandle or globref

Contents of file are slurped


This is called successively to obtain tokens until received undef.

In the Perl spirit of DWIM, new assumes that given an arrayref, you have already done all the work of making your list of whatevers. Given a string (filename) or a file handle, the file is slurped, reading each line of text into a member of the array. Given a callback, the routine is called successively with arguments $p1, $p2, etc. and is expected to return a scalar which is added (pushed on) to the array.


  $lite->apply($lite3, base => 'original');

This method call corresponds approximately to a version control system's check-in function. This causes $lite to be modified, so that its contents now reflect those of $lite2.

$lite does retain the original contents, available via original. However, unlike in a version control system, the object holds only the first original and latest contents.

The VCS::Lite object passed in can also have its own original version. If this is the case, merging will be performed to incorporate the change as if it had come from a different branch. To facilitiate the merging process, optionally specify a base version, which can be the string 'original', 'contents' (the default) or a VCS::Lite object whose contents will be used. This corresponds to the "common ancestor" in version control systems.


This returns a VCS::Lite object for the original version, before changes were applied with apply.


  my $foo = $lite->text;
  my $bar = $lit2->text('|');
  my @baz = $lit3->text;

In scalar context, returns the equivalent of the file contents slurped (the optional separation parameter, defaulting to $_, is used to join the strings together). In list context, returns the list of lines or records.


  my $fil = $lite->id

Returns the name associated with the VCS::Lite element when it was created by new. This is usually the file name.


  my $delt = $lit->delta($lit2);

Perform the difference between two VCS::Lite objects. This object returns a VCS::Lite::Delta object.


This is for backward compatibility with early versions. $lite->diff($lite2) is equivalent to $lite->delta($lite2)->diff.


  my $lit3 = $lit->patch($delt);

Applies a patch to a VCS::Lite object. Accepts a file handle or file name string. Reads the file in diff format, and applies it. Returns a VCS::Lite object for the patched source.


  my $lit4 = $lit->merge($lit1,$lit2,\&confl);

Performs the "parallelogram of merging". This applies two different change streams represented by VCS::Lite objects. Returns a VCS::Lite object with both sets of changes merged.

The third parameter to the method is a sub which is called whenever a merge conflict occurs. This needs to either resolve the conflict or insert the necessary text to highlight the conflict.




At the time of release there is one known bug within VCS-Lite:

Unfortunately Ivor's original svn repository is no longer available, and any work which had done on fixing this bug has now been lost. As time allows I will review the examples and try to implement an appropriate solution.

If you spot a bug or are experiencing difficulties that are not explained within the POD documentation, please send an email to or submit a bug to the RT system (see link below). However, it would help greatly if you are able to pinpoint problems or even supply a patch.

Fixes are dependent upon their severity and my availability. Should a fix not be forthcoming, please feel free to (politely) remind me.


  Original Author: Ivor Williams (RIP)          2002-2009
  Current Maintainer: Barbie <>  2009-2015


  Copyright (c) Ivor Williams, 2002-2006
  Copyright (c) Barbie,        2009-2015


This distribution is free software; you can redistribute it and/or modify it under the Artistic Licence v2.


Colin Robertson for suggesting and providing patches for support of files with unterminated last lines.