---
name: "File::Find::Rule::Extending"
section: "3pm"
platform: "linux"
package: "perl-file-find-rule"
version: "0.35-3"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/File::Find::Rule::Extending"
---

# File::Find::Rule::Extending(3pm)

the mini-guide to extending File::Find::Rule

## NAME

File::Find::Rule::Extending - the mini-guide to extending File::Find::Rule

## SYNOPSIS

```
 package File::Find::Rule::Random;
 use strict;

 # take useful things from File::Find::Rule
 use base 'File::Find::Rule';
 # and force our crack into the main namespace
 sub File::Find::Rule::random () {
     my $self = shift()->_force_object;
     $self->exec( sub { rand > 0.5 } );
 }

 1;
```

## DESCRIPTION

File::Find::Rule went down so well with the buying public that everyone wanted to add extra features.  With the 0.07 release this became a possibility, using the following conventions.

### Declare your package

```
 package File::Find::Rule::Random;
 use strict;
```

### Inherit methods from File::Find::Rule

```
 # take useful things from File::Find::Rule
 use base 'File::Find::Rule';
```

*Force your madness into the main package*

```
 # and force our crack into the main namespace
 sub File::Find::Rule::random () {
     my $self = shift()->_force_object;
     $self->exec( sub { rand > 0.5 } );
 }
```

Yes, we're being very cavalier here and defining things into the main File::Find::Rule namespace.  This is due to lack of imaginiation on my part - I simply can't find a way for the functional and oo interface to work without doing this or some kind of inheritance, and inheritance stops you using two File::Find::Rule::Foo modules together.

For this reason try and pick distinct names for your extensions.  If this becomes a problem then I may institute a semi-official registry of taken names.

### Taking no arguments.

Note the null prototype on random.  This is a cheat for the procedural interface to know that your sub takes no arguments, and so allows this to happen:

```
 find( random => in => '.' );
```

If you hadn't declared `"random"` with a null prototype it would have consumed `"in"` as a parameter to it, then got all confused as it doesn't know about a `'.'` rule.

## AUTHOR

Richard Clamp \<richardc@unixbeard.net\>

## COPYRIGHT

Copyright (C) 2002 Richard Clamp.  All Rights Reserved.

This module is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

## SEE ALSO

File::Find::Rule

File::Find::Rule::MMagic was the first extension module, so maybe check that out.