#!/usr/bin/perl   
use warnings;
use strict;  
my $a=9; my $b=5; my $c=$a*$b;

## Create the folder B in D drive & Save results as Result_File.txt 
#  within B folder:
    
my $output="Result_File.txt";
open (my $fh,">D://B/",$output) or die"Cannot open file'$output'.\n"; # Line 10

print $fh "\n WELCOME! Product of 9 & 5= $c\n\n";

close $output; 
exit;

##</code><code>##

C:\Users\x\Desktop>p5.pl
Unknown PerlIO layer "D" at C:\Users\x\Desktop\p5.pl line 10.
Cannot open file'Result_File.txt'.