new

  my $transform = PPI::Transform->new(
      param1 => 'value1',
      param2 => 'value2',
  );

The "new" constructor creates a new object for your "PPI::Transform" subclass. A default constructor is provided for you which takes no params and creates a basic, empty, object.

If you wish to have your transform constructor take params, these must be in the form of a list of key/value pairs.

Returns a new "PPI::Transform"-compatible object, or returns "undef" on error.

document

The "document" method should be implemented by each subclass, and takes a single argument of a PPI::Document object, modifying it in place as appropriate for the particular transform class.

That's right, this method will not clone and should not clone the document object. If you do not want the original to be modified, you need to clone it yourself before passing it in.

Returns the numbers of changes made to the document. If the transform is unable to track the quantity (including the situation where it cannot tell IF it made a change) it should return 1. Returns zero if no changes were made to the document, or "undef" if an error occurs.

By default this error is likely to only mean that you passed in something that wasn't a PPI::Document, but may include additional errors depending on the subclass.

apply

The "apply" method is used to apply the transform to something. The argument must be a PPI::Document, or something which can be turned into one and then be written back to again.

Currently, this list is limited to a "SCALAR" reference, although a handler registration process is available for you to add support for additional types of object should you wish (see the source for this module).

Returns true if the transform was applied, false if there is an error in the transform process, or may die if there is a critical error in the apply handler.

file

  # Read from one file and write to another
  $transform->file( 'Input.pm' => 'Output.pm' );
  
  # Change a file in place
  $transform->file( 'Change.pm' );

The "file" method modifies a Perl document by filename. If passed a single parameter, it modifies the file in-place. If provided a second parameter, it will attempt to save the modified file to the alternative filename.

Returns true on success, or "undef" on error.