package Mymodule;
{
        use Mouse;
        use Mouse::Util::TypeConstraints;
        use Socket;
...
        subtype 'my_timestamp',
                => as 'Str',
                => where { m/^\d{4}-\d{2}-\d{2} \d{2}:\d{2}:\d{2}$/ },
                => message { 'Not a valid timestamp. Expect: yyyy-mm-dd hh:mm' };
        has 'timestamp' => (
                is => 'ro',
                isa => 'my_timestamp'
		 );