print {$parser->{parameters}[( exists $attr->{':userID'} ? 0 : 1 )]} $parser->ToXML( $tag, $attr);


##</code><code>##

print {$parser->{parameters}[( (exists $attr->{':contents'} and exists $attr->{':contents'}{':userID'}) ? 0 : 1 )]} $parser->ToXML( $tag, $attr);


##</code><code>##

use strict;
use warnings;
no warnings 'uninitialized';

use XML::Rules;

my $parser = XML::Rules->new(
	rules => {
		_default => 'raw',
		'^start_element' => sub {
			my ($tag,$attr,$context,$parents,$parser) = @_;
			$parser->{pad}{found_userID} = 0;
			return 1
		},
		userID => sub {
			my ($tag,$attr,$context,$parents,$parser) = @_;
			$parser->{pad}{found_userID} = 1;
			return [$tag => $attr]
		},
		start_element => sub {
			my ($tag,$attr,$context,$parents,$parser) = @_;

			print { $parser->{parameters}[ $parser->{pad}{found_userID} ] } $parser->ToXML( $tag, $attr), "\n";
		}
	}
);

open my $FH1, '>', 'c:\temp\test1.xml';
open my $FH2, '>', 'c:\temp\test2.xml';
print $FH1 "<root>\n";
print $FH2 "<root>\n";
$parser->parse( \*DATA, [$FH1, $FH2]);
print $FH1 "</root>\n";
print $FH2 "</root>\n";


__DATA__
<root>

<!-- First Element -->
<start_element>

<header>
<element_num>1</element_num>
</header>

<contents>
<child>MyChild</child>
</contents>

</start_element>

<!-- Second Element -->
<start_element>

<header>
<element_num>2</element_num>
</header>

<contents>
<child>MyChild</child>
<userID>MyUser</userID>
</contents>

</start_element>

<!-- Third Element -->
<start_element>

<header>
<element_num>3</element_num>
</header>

<contents>
<child>MyChild</child>
</contents>

</start_element>

</root>


##</code><code>##

my $FH;
if (exists $attr->{':user_id'}) {
  $FH = $parser->{parameters}[0];
} else {
  $FH = $parser->{parameters}[1];
}
print $FH $parser->ToXML( $tag, $attr);
</code></p>

<p>The other script works differently. In the '^start_element' handler it resets the flag (stored in $parser->{pad} which is an attribute of the parser specificaly "to put anything you want to and access it in any handler"), then if the &lt;userID&gt; tag is encountered the flag is set and then the 'start_element' handler selects one of the filehandles passed to <c>$parser->parse()