HTML to DITA through perl

Question

That's the kind of processing I often use XML::Twig for.

The wrap_children method is designed just for this: it lets you define a regexp-like expression that will be wrapped in an element. See the example below and the docs for more:

#!/usr/bin/perl

use strict;
use warnings;

use Test::More tests => 1;

use XML::Twig;

# reads the DATA section, the input doc first, then the expected result
my( $in, $expected)= do{ local $/="\n\n"; <DATA>}; 

my $t=XML::Twig->new->parse( $in);
my $root= $t->root;

# that's where the wrapping occurs, form inside out
$root->wrap_children( '<h3><body>',                   topic => { level => 3 });
$root->wrap_children( '<h2><body><topic level="3">*', topic => { level => 2 });
$root->wrap_children( '<h1><body><topic level="2">*', topic => { level => 1 });

# now we cleanup: the levels are not used any more
foreach my $to ($t->descendants( 'topic'))
  { $to->del_att( 'level'); }

# the wrapping will have generated tons of additional id's, 
# you may not need this if your elements had id's before the wrapping
foreach my $to ($t->descendants( 'topic|body|h1|h2|h3'))  
  { $to->del_att( 'id'); }

# now we can deal with titles
foreach my $h  ($t->descendants( 'h1|h2|h3')) { $h->set_tag( 'title'); }

# how did we do?
is( $t->sprint( pretty_print => 'indented'), $expected, 'just one test');

__DATA__
<doc>
  <h1> Head 1 </h1>
    <body></body>
  <h2> Sub Head 1 </h2>
    <body></body>
  <h3> SubSub Head 1 </h3>
    <body></body>
  <h2> Sub Head 2 </h2>
    <body></body>
  <h1> Head 2 </h1>
    <body></body>
</doc>

<doc>
  <topic>
    <title> Head 1 </title>
    <body></body>
    <topic>
      <title> Sub Head 1 </title>
      <body></body>
      <topic>
        <title> SubSub Head 1 </title>
        <body></body>
      </topic>
    </topic>
    <topic>
      <title> Sub Head 2 </title>
      <body></body>
    </topic>
  </topic>
  <topic>
    <title> Head 2 </title>
    <body></body>
  </topic>
</doc>