...
for my $filename (@file) {
  
   #next unless $filename =~ /^\d+/;
   #if(grep { $seen{$_} =~ $filename} keys %seen) { # Failed
   #if(grep { $filename =~ $seen{$_} } keys %seen) { # Failed
   
if(grep { $filename =~ /\Q$_/ } keys %seen) {
     print " YES - $filename\n";
    } else {
      print " NO  - $filename\n";
    }
}