This program takes two files as parameters, an extract from a LoadRunner script and a subset of the VUGen output, and reconstructs the original XML request.

my $in;
my $request;
my $xml;

# Load request (web_custom_request or soap_request) containing XML
open $in,  '<',  $ARGV[0]      or die "Can't read request file: $!";
$request = do { local $/; <$in> };
chomp $request;

# Extract xml and clean it up
{ # Remove intervening linefeeds and quotes
   local $/;
   $request =~ s/",?\n\s+"//g;
}
$request =~ /(<\?xml.*>)/; # Extract the XML...
$xml = $1; # ...into a local variable
$xml =~ s/\\"/"/g; # De-escape the quotes
$xml =~ s/\\r\\n/\n/g; # Convert "\r\n" into newline

# Substitute parameters
open(PARAMS,  $ARGV[1]) or die "Can't read params file: $!";

# For every line in the parameter file
for (<PARAMS>) {
   if (/"(.+)" =  "(.*)"/) { # Is it a real parameter line?
      my $key = $1; # Save key name
      my $value = $2; # Save value to substitute
      my $count = $xml =~ s/{$key}/$value/; # Replace the {parameter}
   }
}

print $xml;