MACRO and BLOCK are also quite useful. You can use them to build recursive template routines. Don't like the word routine here, but it kinda fits.

builds a string containing the number of "A"'s specified. (dumb example, and it may not work, not tested, but you get the idea) I'm ignoring the argument for/against doing this in template code. The HTML::Template guys will put a hit out on me. :)

[% MACRO gen_a_list(number_of_as) BLOCK %]
  [% a_string = "" %]
  [% IF number_of_as > 0 %]
    [% a_string = "A" _ gen_a_list(number_of_as - 1) %]
  [% END %]
  [% a_string %]
[% END %]
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I really enjoy working with TT. I haven't checked out the book yet. Is it decent?