Splitting on uppercase, not lowercase

workflow/main.nf

@@ -43,7 +43,7 @@ process tolines {
     file "${uppercase.name}.tolines" into tolines
 
     """
-    cat "$uppercase" | tr -cs "a-z'" "\012"  > "${uppercase.name}.tolines"
+    cat "$uppercase" | tr -cs "A-Z'" "\012"  > "${uppercase.name}.tolines"
     """
 
 }