Revert "syntax: Remove empty rules in regions"

This reverts commit a9b513a28a.

runtime/syntax/perl.yaml

@@ -28,10 +28,12 @@ rules:
         start: "'"
         end: "'"
         skip: "\\\\'"
+        rules: []
 
     - comment:
         start: "#"
         end: "$"
+        rules: []
 
     - constant.string: "\"\\(.*\\)\"|qq?\\|.*\\||qq?\\{.*\\}|qq?\\/.*\\/"
     - constant.number: "\\b([0-9]*[.])?[0-9]+"
@@ -43,11 +45,14 @@ rules:
     - preproc:
         start: "(^use| = new)"
         end: ";"
+        rules: []
 
     - comment:
         start: "^="
         end: "^=cut"
+        rules: []
 
     - identifier.macro:
         start: "<< 'STOP'"
         end: "STOP"
+        rules: []