sub add_cr
  { my %source= @_;
    my $content; # I suppose eventually that's what you want
    if( $source{content} 
      { # content is in $source{content}
      }
    elsif( my $content_ref= $source{ref})
      { # content in $$content_ref
      }
    elsif( my $filename= $source{filename})
      { # you get the idea?...