use warnings;
use strict;
open (my $fh, '<', "data.txt") or die "could not open dirs.log $!;

 
while (my $line=<$fh>) {
$key = lc($line);
$Hash{$key}=$line;
}

open my $hash, '>', "hash.txt";
print $hash Dumper( \%Hash );
close $hash;