I need to be able to search a binary file for a string of hexadecimal characters and then prompt the user so they can decide if they want to change it. If they enter a "y" then the program changes the string and prints the change to the new file, if they enter a "n" then the program moves on to the next match. The goal is to create an identical file except where the program has replaced the search string with 00s. You can download an example of a file I would be modifying from:

http://members.lycos.co.uk/jfulley/example.bin

You're going to have to copy and paste the location into your browser since it's hosted on a free website.

The program below stops responding after it finds the first string match and prompts the user for a response. As soon as you enter a y or n the program stops responding. 

$original = &promptUser("Enter original filename");
$modified = &promptUser("Enter modified filename");

open($ORIG, "$original");
binmode($ORIG);

open($MOD, ">$modified");
binmode($MOD);

$/ = "\x00";

while (<$ORIG>) {

$count = (($change = $_) =~ s/(\x33\x33\x39\x39.*?\x00)/"\x00" x lengt
+h($1)/e);

if ($count == null) {

print $MOD $_;

} else {

    $answer = &promptUser("Modify $1?");
    if ($answer == "y") {
    print $MOD $change;
    } else {
    print $MOD $_;
    }

}
}

close $MOD;
close $ORIG;

sub promptUser {

   local($promptString,$defaultValue) = @_;

   if ($defaultValue) {
      print $promptString, "[", $defaultValue, "]: ";
   } else {
      print $promptString, ": ";
   }

   $| = 1;               # force a flush after print
   $_ = <STDIN>;         # get the input from STDIN

   chomp;

   if ("$defaultValue") {
      return $_ ? $_ : $defaultValue;    # return $_ if it has a value
   } else {
      return $_;
   }
}

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