open (IN, 'file.txt');
my $out = '';
my $newComment = 0;
while (<IN>) 
{
    if(($newComment < 1) && ($_ ne /^\#|^--|^\/\/^\s*\/\*/|^\s*\*|\*\/$/))
   {
     $out .= "#This file was updated with the fix"; 
     $out .= "\n";
     $newComment++; 
   }   

    $out .= $_;
}
open (OUT, '>output.txt');
print OUT $out or die "Can't print to OUT: $!";
close OUT;
close IN;

__DATA__
/*
* This is the new function
 * It has the following parameters:
 *
 * 1. Filename 
*  2. URL
*/  
# All the following are valid comment styles:
# hello perl style
-- hello sql style
/* hello c style
 * continue c style
   end c style */
// c++ c style
#Revision date: 2005-10-10
--start of file
<--  here is where the new comment should go.

configurationtype=search
url=http://www.google.com


--End of file