There is a foible in the following code that may be an XML::Twig bug, but aside from that the following may help:

use strict;
use warnings;
use XML::Twig;

my $org = <<XML;
<TEI>
 <head>Note VII</head>
 <head>Title Page </head>
 <head>Note VII</head>
 <head>Preface </head>
 <head>Copyright Page </head>
</TEI>
XML

my $mod = <<XML;
<TEI>
 <head>Note <romanNumeral>VII</romanNumeral></head>
 <head>Title Page </head>
 <head>Copyright Page </head>
 <head>Preface </head>
</TEI>
XML

my $twig = XML::Twig->new (twig_roots => {'head' => \&fetchNode,});
my %subs;

$twig->parse ($mod);
$twig->purge ();

$twig = XML::Twig->new (
    twig_roots               => {'head' => \&editNode,},
    twig_print_outside_roots => 1
);

$twig->parse ($org);
$twig->flush ();


sub fetchNode {
    my ($t, $elt) = @_;
    my $text = $elt->text ();

    $subs{$text} = $elt;
    $t->purge ();
}


sub editNode {
    my ($t, $elt) = @_;
    my $text = $elt->text ();

    $subs{$text}->replace ($elt);
    $t->flush      ();
}

[download]

Prints:

<TEI>
 <head>Note <romanNumeral>VII</romanNumeral></head>
 <head>Title Page </head>
 <head>Note <romanNumeral>VII</romanNumeral></head>
 <head>Preface </head>
 <head>Copyright Page </head>
</TEI>
</TEI>

[download]

Note the nested root noderepeated close tag! This code doesn't care if the order of the nodes has changed or if nodes have been added in the main document, but that probably doesn't matter.

Update updating XML::Twig to 3.32 produces a slightly different result which can be corrected by removing the flush following $twig->parse ($org);.

Perl reduces RSI - it saves typing

In reply to Re: Swapping xml elements from an external file? by GrandFather
in thread Swapping xml elements from an external file? by tonyz

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