Answer using Moo

# oo.t

use strict;
use warnings;
use lib '.';
use Test::More;

use_ok 'Service', 'Service.pl loads';

my $xml = Service->new_by_name('xml', 'xmldata');
$xml->populate;
is $xml->template, '<data>xmldata</data>', 'XML OK';

my $json = Service->new_by_name('json', 'jsondata');
$json->populate;
is $json->template, '{"data": jsondata}', 'JSON OK';

done_testing;


# Service.pm
package Service;

use Moo;

has 'data'      => (is => 'ro', required => 1);
has 'template'  => (is => 'rw', builder => '_build_template');

sub populate {
    my $self = shift;
    (my $tmpl = $self->template) =~ s/\[data\]/$self->data/emsi;
    $self->template($tmpl);
}

sub new_by_name {
    my (undef, $name, $data) = @_;
    $name = uc $name;
    my $class = __PACKAGE__ . "::$name";
    eval "require $class";
    $class->new(data => $data);
}

1;


# Service/XML.pm
package Service::XML;

use Moo;
extends 'Service';

sub _build_template { '<data>[data]</data>' }

1;


# Service/JSON.pm
package Service::JSON;

use Moo;
extends 'Service';

sub _build_template { '{"data": [data]}' }

1;
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Answer using MooX::Pression

In this example, Service/XML.pm and Service/JSON.pm are no longer needed; all classes are defined in Service.pm.

use MooX::Pression prefix => 'MyApp';

class ::Service {
    has data     (is => ro, type => Str, required => true);
    has template (is => rw, type => Str, builder => true);
    
    method populate () {
        (my $tmpl = $self->template) =~ s/\[data\]/$self->data/emsi;
        $self->template($tmpl);
    }
    
    method new_by_name (Str $name, Str $data) {
        $name = uc $name;
        my $child = "$class\::$name";
        $child->new(data => $data);
    }
    
    class +XML {
        method _build_template () { '<data>[data]</data>' }
    }
    
    class +JSON {
        method _build_template () { '{"data": [data]}' }
    }
}

1;
[download]