The part: $xml = "<?xml version="1.0"?> can't work, as you use ". Maybe this is your problem?

Try to use something like this:

my $xml=<<'XML';
<?xml version="1.0"?>
<?xml-stylesheet type="text/xsl" href="/templates/xsl/abc/search/searc
+hRetrieveResponse.xsl"?><searchRetrieveResponse xmlns="http://www.abc
+/srw/">
   <version>1.1</version>
   :
   :
XML
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