Embed Perl With Mason -- Read All About It

autarch writes "Embedding Perl in HTML with Mason, written by Ken Williams and me, is now available at booksellers of distinction. Mason is a Perl-based templating system and application framework. The book covers Mason from the basics on up to extending the Mason core with your own subclasses. For more details check out our web site and the O'Reilly site. The latter includes the TOC and a sample chapter."

Comments

Get it cheaper

[RedWolves2]

Amazon has it for $24.47

Re:Readability?

[scrytch]

Consider Template Toolkit instead. The above example transliterated looks like:

[% noun = 'World' %]
[% PERL %]
# perl ugliness, but there may be a tt2 split op. note cache means nothing like mason's cache
@{$cache->{time}} = split /[\s:]/, localtime;
[% END %]
Hello $noun,
[% IF time[3] < 12 %]
good morning
[% ELSE %]
good afternoon
[% END %]

Mind you, I'd have put it in variables in another block, so the message would look like:

Hello $noun, $greeting

I personally don't use the $foo syntax, and prefer [% foo %] instead, but TMTOWTDI in TT2. TT2's power just blows mason away, and it's not all that difficult to get it doing mason-like persistence things when you combine it with Tie::MLDBM.

Re:Readability?

[scrytch]

> So, what features and/or functionality in TT is so much better than Mason in your opinion?

The internals of TT2 are amazingly hackable, and provide one of the most useful examples of OOP reuse. It's like a textbook study in design patterns that work. For example, it took me only a few hour's hacking to subclass one class (I forget the name, it's been a while) to create mason-like search behavior for [% INCLUDE %]. Just syntax-wise, TT2 tends to look cleaner -- you don't have to have weird looking noise like <% } > ending all your blocks. You can even change the delimiters from [% foo %], e.g. the metatext %%foo%%, mason's lt;% foo %> or anything else you want, within reason (the parser can get confused).

Anyway, all those intangibles aside, TT2 is a complete language in its own right -- looks a bit like python, come to think of it -- so you can do even complex logic without embedding perl. When you do embed perl, you can simply 'print' in a perl block, and it will be output to the HTML (I wrote that part, though it's admittedly pretty trivial). In mason, you have to append to a string. If you need to really mess with the internals, you can embed [%RAWPERL%] blocks that are a straight eval. You can enable and disable PERL and RAWPERL blocks from the invocation, a nice way to set policy when using it in mod_perl.

TT2 has INCLUDE not just for files, but for BLOCK definitions as well. You not only can define blocks, but functions and macros in the TT2 language. You can include arbitrary perl modules and use them in the TT2 language. You can take the output of any block and filter it with user-defined processors using unix pipe syntax. With [%WRAPPER%] you can do a reverse-include, taking the current doc and including it as the value of a magic variable in another document. Variables defined in the TT2 language have lexical scope, and you can choose to include a template in a new scope with [%INCLUDE%] or in the current scope with [%PROCESS%]. TT2 even has some amount of OOP, with [%VIEW%] constructs, which are sort of blocks on steroids. I still haven't completely wrapped my head around views, and they're still kind of primordial at this time, but they seem to be aimed at Mason's strength: components.

Mason's component model is still superior to TT2, and I was writing a mod_perl system for TT2 that would have addressed that, but I haven't been too active with it lately (read: the year and a half or so). Mostly I've been pining for someone to port TT2 to python, actually. I don't see it as a contest of "Mason sucks, TT2 rules", I just have personal preferences, and would gladly like to see both systems giving each other healthy competition.

BTW, Slash uses TT2, though not nearly to its full potential.