use CGI(qw(:standard));
use strict; 
use XML::Writer;
use IO::File;

#Übergabeparameter
my $user=(param('user')||"");
my $query=(param('query')||"");
my $type = (param('type')||"");
my $filename = param('filename')||"";
User_config($user);

$filename .= ".wsdl";
my $output = new IO::File(">$filename");

my $writer = new XML::Writer(OUTPUT => $output);

$writer->startTag("wsdlitem");
$writer->startTag("id");
$writer->characters($type);
$writer->endTag("id");
$writer->startTag("query");
$writer->characters($query);
$writer->endTag("query");
$writer->endTag("wsdlitem");
$writer->end();

$output->close();


#öffnet html Code und weist ihn einer Variable zu
open (WSDL, "$html_path/addWSDL.html");
my $content=join ('',<WSDL>);
close WSDL;

$content=~s/\$img_URL/$img_URL/g;
$content=~s/\$user/$user/g;
$content=~s/\$l_title/$l_title/g;
$content=~s/\$l_store/$l_store/g;
$content=~s/\$l_cancel/$l_cancel/g;
$content=~s/\$query/$query/g;
$content=~s/\$type/$type/g;
$content=~s/\$filename/$filename/g;

print header();
print $content;

use CGI(qw(:standard));
use strict;
...

if (param) {  ### HIER!
#Übergabeparameter
my $user=(param('user')||"");
...

$filename .= ".wsdl";
my $output = new IO::File(">$filename");
my $writer = new XML::Writer(OUTPUT => $output);
...
$writer->end();
...
$output->close();

}
else { #### UND HIER DANN
#öffnet html Code und weist ihn einer Variable zu
open (WSDL, "$html_path/addWSDL.html");
my $content=join ('',<WSDL>);
close WSDL;
...
print header();
print $content;
}

if ( $ENV{REQUEST_METHOD} eq 'POST') {
   # schreibe XML
}