As prasadbabu given correct answer I believe.

As of my understand you want the last potion from the line which begins with Note. I also done this with split function.

use strict;
use warnings;
my $x;
while($x=<DATA>){
    chomp($x);
    if ($x =~ /^\[Note\]/){
    my $find=(split(/\,/,$x))[-1] ;
    print "$find\n";                                                  
+                                                                     
+  
    }

}
__DATA__
[Note]note_values,notes_values2
[Book]novels,magazines
[Note]note_values,notes_values56
[download]