accessing the entire stream

I want to manipulate various href links in the server response. I read in
the server response as follows:

sub handler
{
  my $f = shift;
  unless ($f->ctx){
    while ($f->read(my $Buffer, BUFF_LEN)) {
      if ($Buffer =~ m/Logout/){
        $Buffer =~ s/href="(.*?\?.*?)"/href="$1\&NewParameter=$Value"/g;
        $f->print($Buffer);
    }
    return Apache2::Const::OK;
   }
  }
}

The BUFF_LEN constant is set to 1024. I want to run the regex against the
entire server response. I tried adding a $CompleteBuffer .= $Buffer inside
the while loop and moving the $f->print($Buffer) statement out of that loop,
but still ended up with multiple copies of the same text within $Buffer.
What is the correct what to access the entire server response in a single
variable? Any pointers to examples of this are greatly appreciated.

Thanks,
Chris