use strict;
use warnings;

package MakeObject;
use Data::Dumper;

my $rootDir = '/home';
my $userId  = 'smith';
my $appName = 'project';

my $obj = MakeObject->new;

printf "Object contents => %s\n", Dumper($obj);

sub new {
    my $obj = bless {
        Root        =>  $rootDir, 
        UserDir     => "$rootDir/Usr/$userId/",
        UserAppData => "$rootDir/Usr/$userId/$appName/",
    }, shift;

    return $obj;
}

__END__
Output is:

Object contents => $VAR1 = bless( {
                 'Root' => '/home',
                 'UserDir' => '/home/Usr/smith/',
                 'UserAppData' => '/home/Usr/smith/project/'
               }, 'MakeObject' );