Hello world (from command-line)

After installing Mason, you should have a "mason" command in your installation path (e.g. "/usr/local/bin"). Try this:

    % mason
    Hello! The local time is <% scalar(localtime) %>.
    ^D

(where '^D' means ctrl-D or EOF). You should see something like

    Hello! The local time is Wed Mar  2 17:11:54 2011.

The "mason" command reads in a Mason component (template), runs it, and prints the result to standard output. Notice that the tag

    <% scalar(localtime) %>

was replaced with the value of its expression. This is called a substitution tag and is a central piece of Mason syntax.

Email generator (from script)

The command line is good for trying quick things, but eventually you're going to want to put your Mason components in files.

In a test directory, create a directory "comps" and create a file "email.mc" with the following:

    <%class>
    has 'amount';
    has 'name';
    </%class>
    Dear <% $.name %>,
        We are pleased to inform you that you have won $<% sprintf("%.2f", $.amount) %>!
    Sincerely,
    The Lottery Commission
    <%init>
    die "amount must be a positive value!" unless $.amount > 0;
    </%init>

In addition to the substitution tag we've seen before, we declare two attributes, "amount" and "name", to be passed into the component; and we declare a piece of initialization code to validate the amount.

In the same test directory, create a script "test.pl" with the following:

     1  #!/usr/local/bin/perl
     2  use Mason;
     3  my $interp = Mason->new(comp_root => 'comps', data_dir => 'data');
     4  print $interp->run('/email', name => 'Joe', amount => '1500')->output;

Line 3 creates a Mason interpreter, the main Mason object. It specifies two parameters: a component root, indicating the directory hierarchy where your components will live; and a data directory, which Mason will use for internal purposes such as class generation and caching.

Line 4 runs the template - notice that the ".mc" extension is added automatically - passing values for the "name" and "amount" attributes.

Run "test.pl", and you should see

    Dear Joe,
        We are pleased to inform you that you have won $1500.00!
    Sincerely,
    The Lottery Commission