open (my $readhandle, "<", $filetoread) 
  or die "Unable to read '$filetoread': $!";

open (my $writehandle,"+>", $filetowrite) 
  or die "Unable to write '$filetowrite': $!";

open (my $outputhandle, ">", $fileoutput)
  or die "Unable to write '$fileoutput': $!";