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

my $files = "C:/Directory";
my $list  = "C:/Test.sdf";

my %keepList;

open my $namesIn, '<', $list or die "Failed to open file: $!\n";

# minor updates to this loop #####################

while (my $line = <$namesIn>) #updated #######
{
   my $sdf_file;
   #next unless ($sdf_file) = $line =~ /(\w+\.nfo)"$/;
   #this regex should work equally well
   next unless ($sdf_file) = $line =~ /(\w+\.nfo)/;
   $keepList{$sdf_file} = 1;
   print "keeping $sdf_file\n"; #update for debugging #######
}
close $namesIn;

opendir my ($filesScan), $files or die "unable to open dir $!";

while (my $filename = readdir $filesScan) 
{
    next unless -f "$files/$filename";  #only simple files allowed
                                        #skip . and .. or other dirs
    next if exists $keepList{$filename};
    
    unlink "$files/$filename" or warn qq{cannot delete $filename: $!+};
}

closedir $filesScan;