my $obj = Class->new;
$obj->a_method($param1, $param2..., $paramN);

##</code><code>##

package My::Daemon;

use strict;
use warnings;
use Frontier::Daemon;

sub new {
  my($class, @args) = @_;
  ....
  my $self = {}; # empty anonymous HASH ref
  bless $self, $class; # make it an object and return it
}

sub some_method {
  my $self = shift;
  my $id = Frontier::Daemon->new(
    methods => {
      sum => sub { # anonymous sub as callback
        my @args = @_; # @args received from F::D somewhere
        ....
        $self->sum(@args); # call sum as object method
      },
    },
    ... other params
  );
}

sub sum {
  my($self, $arg1, $arg2) = @_;
  ...
}

1;