#! /usr/bin/perl
use strict;
use warnings;
use XML::Parser;

{
    my $is_article = 0;

    sub handle_start {
        my ( $expat, $element, %attr ) = @_;

        if ( $element eq 'article' ) {
            $is_article = 1;
        }
        elsif ( $is_article ) {
            print $expat->original_string;
        }
    }

    sub handle_end {
        my ( $expat, $element, %attr ) = @_;

        if ( $element eq 'article' ) {
            $is_article = 0;
        }
        elsif ( $is_article ) {
            print $expat->original_string;
        }
    }

    sub handle_char {
        my ( $expat, $string ) = @_;

        #print $expat->original_string if $is_article;
        print $string if $is_article;
    }
}


my $x = XML::Parser->new();

$x->setHandlers(
    Start => \&handle_start,
    End   => \&handle_end,
    Char  => \&handle_char,
);

$x->parse( *DATA );

__DATA__
<document>
    <article>
        Hello
        <foo>Foo</foo>
        World
    </article>
    <article>
        Hello
        <bar>Bar</bar>
        World
    </article>
</document>