maybe a second attempt is better than first one. I had to specify what an hostname is in an ugly way but seems viable.

I'm going mad to understand why the dot . is passed in for IPs and not for hostnames! (because ip ends with an action?)

#!/usr/bin/env perl
use warnings;
use strict;

use Data::Dump;
use Marpa::R2;

my $rules = <<'END_OF_GRAMMAR';
lexeme default = latm => 1
:default ::= action => ::first

entry           ::= op hostaddr4    action => dump_entry
op              ::= 'add'           action => add_op
                  | 'remove'        action => add_op
                  
hostaddr4       ::= hostname | ipv4


hostname        ::= DOMAIN  EXT               action => add_hostname
                  | DOMAIN DOMAIN EXT         action => add_hostname
                  | DOMAIN DOMAIN DOMAIN EXT  action => add_hostname

DOMAIN          ::= NAME '.'
NAME            ~ [\d\w]+
EXT             ~ 'org' | 'net'                 

ipv4            ::= NUMBER '.' NUMBER '.' NUMBER '.' NUMBER action => 
+add_ip                    
NUMBER          ~ [\d]+
                    
:discard        ~ SP
SP              ~ [\s]+    


END_OF_GRAMMAR

my $input = <<'END_OF_INPUT';
add example.org
add www.perl.org
add 42.perl.net
add 192.0.2.1
remove 192.0.2.2

END_OF_INPUT

my $grammar = Marpa::R2::Scanless::G->new({source => \$rules});

for (split /^/m, $input) {
    chomp;
    if (length $_) {
        print "\nPARSING: $_\n";
        
        my $recce = Marpa::R2::Scanless::R->new({
            grammar => $grammar, 
        });
        my $value_ref = $grammar->parse( \$_, 'main');
    }
}

sub dump_entry{
    print "dump_entry received: "; dd shift @_;
}

sub add_op{
    my $self = shift @_;
    print "add_op received: "; dd @_;
        $$self{operator} = join '',@_;
    return $self;
}

sub add_ip{
    my $self = shift @_;
    print "add_ip received: "; dd @_;
        $$self{type} = 'IP';
    $$self{value} = join '',@_;
       return $self;
}
sub add_hostname{
    my $self = shift @_;
    print "add_hostname received: "; dd @_;
        $$self{type} = 'hostname';
    $$self{value} = join '.',@_;
        return $self;
}
__DATA__

PARSING: add example.org
add_op received: "add"
add_hostname received: ("example", "org")
dump_entry received: { operator => "add", type => "hostname", value =>
+ "example.org" }

PARSING: add www.perl.org
add_op received: "add"
add_hostname received: ("www", "perl", "org")
dump_entry received: { operator => "add", type => "hostname", value =>
+ "www.perl.org" }

PARSING: add 42.perl.net
add_op received: "add"
add_hostname received: (42, "perl", "net")
dump_entry received: { operator => "add", type => "hostname", value =>
+ "42.perl.net" }

PARSING: add 192.0.2.1
add_op received: "add"
add_ip received: (192, ".", 0, ".", 2, ".", 1)
dump_entry received: { operator => "add", type => "IP", value => "192.
+0.2.1" }

PARSING: remove 192.0.2.2
add_op received: "remove"
add_ip received: (192, ".", 0, ".", 2, ".", 2)
dump_entry received: { operator => "remove", type => "IP", value => "1
+92.0.2.2" }
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