Is the $file being passed in a filename or a reference ? If it is just a filename, then "set file to the value of $self->{file} already bound." won't work since the value doesn't get back to the caller.

Maybe what you want is for the call in the program to obj->file("Filename"); to store the filename internally, and my $fn = obj->file(); to return it.

If so, your code needs to look more like :

sub filename
{
   my ($self, $file) = @_;

   $self->{file} = $file if $file;

   return $self->{file};
}
[download]

to get the file back to the caller.

I don't like the $self->{'file'} = shift || $self->{'file'}; idea, since setting something to itself when you don't need to is less clear.
--
Brovnik