Variable references belonging to the parent scope added ('@')

scanner.go

@@ -7,6 +7,7 @@ package expr
 import (
 	"bufio"
 	"errors"
+	"fmt"
 	"io"
 	"strconv"
 	"strings"
@@ -190,7 +191,17 @@ func (self *scanner) fetchNextToken() (tk *Token) {
 		case '#':
 			tk = self.makeToken(SymHash, ch)
 		case '@':
-			tk = self.makeToken(SymAt, ch)
+			if next, _ := self.peek(); (next >= 'a' && next <= 'z') || (next >= 'A' && next <= 'Z') {
+				self.readChar()
+				if tk = self.fetchIdentifier(next); tk.Sym == SymIdentifier {
+					//tk.Sym = SymIdRef
+					tk.source = "@" + tk.source
+				} else {
+					tk = self.makeErrorToken(fmt.Errorf("invalid variable reference %q", tk.source))
+				}
+			} else {
+				tk = self.makeToken(SymAt, ch)
+			}
 		case '_':
 			tk = self.makeToken(SymUndescore, ch)
 		case '=':