I'm guessing your real intention is to check for well-formedness. The question also implies you're doing XML parsing in a fragile way elsewhere. If I'm right, the following might be a good start to doing things in a way that's more bomb-proof and easier to extend. See XML::LibXML for more.

use XML::LibXML;

local $/ = "::FILE::";

my $parser = XML::LibXML->new();
# $parser->recover(1); <-- turn on to "save" many bad docs.

while ( my $xml = <DATA> )
{
    chomp($xml);
    my $doc = eval { $parser->parse_string($xml) };
    if ( $doc )
    {
        print "File $. is valid.\n";
        # Do whatever you want with your valid $doc here.
    }
    else
    {
        print "File $. is NOT valid.\n";
        # Deal with bad docs here...
    }
}

__DATA__
<order>
 <customer>
  <name>Coyote, Ltd.</name>
  <shipping_info>
    <address>1313 Desert Road</address>
    <city>Nowheresville</city>
    <state>AZ</state>
    <zip>90210</zip>
  </shipping_info>
 </customer>
 <item>
  <product id="1111">Acme Rocket Jet Pack</product>
  <quantity type="each">1</quantity>
 </item>
 <item>
  <product id="2222">Roadrunner Chow</product>
  <quantity type="bag">10</quantity>
 </item>
 </order>

::FILE::

<order>
 <customer>
  <name>Coyote, Ltd.</name>
  <shipping_info>
    <address>1313 Desert Road</address>
    <city>Nowheresville</city>
    <state>AZ</state>
    <zip>90210</zip>
  </shipping_info>
 </customer>
 <item>
  <product id="1111">Acme Rocket Jet Pack</product>
  <quantity type="each">1</quantity>
 </item>
 <item>
  <product id="2222">Roadrunner Chow</product>
  <quantity type="bag">10</quantity>
 </item>
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