use strict;
use warnings;
 
my $filename = 'dirtest.txt';
open(my $fh, '<:encoding(UTF-8)', $filename)
  or die "Could not open file '$filename' $!";
 
while (my $row = <$fh>) {
  chomp $row;
  next if $row =~ /.{20}\\[a-zA-Z]\s[\r\n]/;
  print "$row\n";
}
[download]

The following is the file content:

 Directory of D:\ \Q\X

09/20/2019  07:57 PM    <DIR>          .
09/20/2019  07:57 PM    <DIR>          ..
[download]

The regex works for this content in online regex https://regex101.com/r/LFrvLp/11 But when I run the script, EVERY row is displayed, it should only be the FIRST row as it is the only row with a backslash in position 21.