Allow whitespace surrounding the root tag, empty arrays and tuples, and literal backslashes in strings

src/drv.pegjs

@@ -1,5 +1,8 @@
 start
-	= deriveTag
+	= _ root:deriveTag _ { return root; }
+
+_
+	= [ \n\r\t]*
 
 value
 	= deriveTag
@@ -8,7 +11,7 @@ value
 	/ string
 
 multipleItems
-	= item:value subsequentItems:("," value)* { return [item].concat(subsequentItems.map(subsequentItem => subsequentItem[1])); }
+	= item:value? subsequentItems:("," value)* { return (item != null) ? [item].concat(subsequentItems.map(subsequentItem => subsequentItem[1])) : []; }
 
 deriveTag
 	= "Derive(" items:multipleItems ")" { return {type: "deriveTag", items: items}; }
@@ -23,8 +26,9 @@ string
 	= '"' chars:stringCharacter* '"' { return chars.join(""); }
 
 stringCharacter
-	= !('"' / "\\") char:. { return char; }
+	= !('"' / "\\") char:. { return char; }  // Prefer a non-backslash character...
-	/ stringEscapedQuote { return '"'; }
+	/ stringEscapedQuote { return '"'; }     // ... then an escaped quotation mark...
+	/ !('"') char:. { return char; }         // ... and finally any other character that doesn't terminate the string.
 
 stringEscapedQuote
 	= '\\"'