Hi QuillMeantTen, I am only addressing your last comment: if you have any suggestions toward making my code more readable/maintainable or at least less eye-gouging ... since you asked.

I would make use of blank lines and spaces and quoted hash key names to improve readability. Of course there's a tradeoff in less code being viewable on a screen, but for me, it's faster to scroll (<CTRL-F>, <CTRL-B> ?) than to try to decipher overly compact source code. My eyes literally don't distinguish the point on the curly brace if it's butted up against a parenthesis. But I'm old. For example I would write:

    foreach my $key (@keys){
        if(!defined($self->{output}->{$key}->{fh}) && !$self->{output}
+->{$key}->{type}  eq
        'named_pipe'){
            croak "undefined fh for key $key\n";
        }
        given($self->{output}->{$key}->{type}){
            when('named_pipe'){
                open my $handle ,'>',$self->{output}->{$key}->{name} o
+r croak "could
                not open output handle";
                print $handle $input;
                close $handle;
            }
            
            # when ...
        }
    }
[download]

as this:

  foreach my $key ( @keys ) {

    if ( ! defined ( $self->{'output'}->{$key}->{'fh'} )
         && $self->{'output'}->{$key}->{'type'} ne 'named_pipe' ) {
      croak "undefined fh for key $key\n";
    }

    given ( $self->{'output'}->{$key}->{'type'} ) {

      when ('named_pipe') {
        open my $handle, '>', $self->{'output'}->{$key}->{'name'}
          or croak "open failed: $!";
        
        print $handle $input;
        close $handle or croak "close failed: $!";
      }

    }

  }
[download]

Alternatively sometimes readability trumps memory usage and I might make a copy of a variable if I was going to be using it a few times, and its current name was unwieldy, especially if that meant I could avoid splitting statements over two lines:

  foreach my $key ( @keys ) {

    my $foo = $self->{'output'}->{$key};

    if ( ! defined $foo->{'fh'} and $foo->{'type'} ne 'named_pipe' ) {
      croak "undefined fh for key $key\n";
    }

    given ( $foo->{'type'} ) {

      when ('named_pipe') {
        open my $handle, '>', $foo->{'name'} or croak "open failed: $!
+";
        print $handle $input;
        close $handle or croak "close failed: $!";
      }

    }

  }
[download]

There you go; this advice is definitely worth what it cost you :-)

Update: removed a pair of artefactal parens