I've read off and on that when you make an object oriented package, that you should not force poop on people. That it should be an opton, not a default.

So, my first thoughts were ... I guess if my package has method hello(), then there should be a _hello() which is the functional oriented equivalent. Seems silly.. And I have a gut feeling there's various tricks to have a sub act as both a functional oriented, and object oriented subroutine.

I patched this together and it seems to work well. Here's my example:

use Carp;
use constant haveyaml => ( eval 'require YAML;' ? 1 : 0 );
my $META_HIDDEN=1; sub META_HIDDEN : lvalue { $META_HIDDEN }
my $META_EXT = 'meta'; sub META_EXT : lvalue { $META_EXT }

sub set_meta {
    my $abs_path = shift;

    if (ref $abs_path eq __PACKAGE__){
        $abs_path = $abs_path->abs_path;
    }        

    my $meta = shift; 
    ref $meta eq 'HASH'
        or croak('second argument to set_meta() must be a hash ref');
    
    haveyaml or 
          carp 'set_meta() cant be used, '
          .'YAML is not installed.' and return;

    $abs_path=~s/^(.+\/)([^\/]+$)/$1.$2/ if META_HIDDEN;

    unless( keys %$meta){
        unlink $abs_path .'.'.META_EXT;
        return 1;
    }
    
    YAML::DumpFile($abs_path .'.'.META_EXT,$meta);    
    return 1;
}

[download]

So this sub can be used as $object->set_meta($hashref) or set_meta($path,$hashref). The way to detect here is to see if the first argument is a ref to the package, or not.

I've looked for examples of having subroutines act as both object oriented and functional oriented code, and I came up kind of empty, maybe I'm not looking right.

Any suggestions how else to do this? How to have a subroutine detect if it's being used as a method or a normal subroutine?

And uhm.. If I can also ask.. Is setting that constant to check for YAML really bad? Or too taxing on the sytem?

update
Using a subroutine as both procedural function and oo method can create problems with inheritance (and complexity). Thanks to the discussion, I can with confidence put this aside and move on. Verdict is nonono. I'll use different subs, some for oo some for procedural.

In reply to coding a subroutine as both method and regular function by leocharre

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