Some comments.

diff --git a/pl.py b/pl.py
index f5d7bbe..79a5fe2 100755
--- a/pl.py
+++ b/pl.py
@@ -187,9 +187,11 @@ def playlist_is_ok(playlist, options):
         # this is not a problem to be reported globally, we return True
         return True
     else:
+        # some inits
         missing_items = set()
         if options.delete or options.fix:
             new_playlist = []
+        # now start checking item by item
         for item in items:
             item = item.strip()
             # ignore empty and commented lines