Perhaps the following will assist:

#!/usr/bin/perl   
use warnings;
use strict;

my $a = 9;
my $b = 5;
my $c = $a * $b;

my $dir    = 'D:/B';
my $output = 'Result_File.txt';

## Create the folder B in D drive & Save results as Result_File.txt
#  within B folder:

mkdir $dir or die $!;

open my $fh, '>', $dir . '/' . $output or die "Cannot open file '$outp
+ut'.\n";    # Line 10

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

close $fh;
[download]

• perltidy was used to reformat the script.
• As Athanasius suggested, mkdir was used to create the directory. Also, the file handle was closed.
• And as LanX suggested, a three-argument open was used (and perhaps you meant something like open (my $fh,">D:/B/$output") ...).

Hope this helps!

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