use warnings;
use strict;

use File::Find::Rule;

my $path = 'c:/sdf'; # path to look in
my $sdf_file = 'c:/sdf_file.txt';

open my $fh, '<', $sdf_file
  or die "can't open the flippin' flackin' file!: $!";

my @sdf_files;

while (<$fh>){
    chomp;

    if (my ($file) = /fullpath="(.*)"$/){
        # replace backslash to fwd slash, and lowercase
        $file =~ s|\\|/|g;
        $file = lc $file;
        push @sdf_files, $file;
    }
}

my @files = File::Find::Rule->file()
                            ->name('*.sdf')
                            ->in($path);

for my $file (@files){
    $file = lc $file;
    if (! grep {$file eq $_} @sdf_files){
        print "deleting $file\n";
        unlink $file or die $!;
    }
}