config/lang: escaping interpolations with double dollar signs

config/lang/lex.go

@@ -299,9 +299,19 @@ func (x *parserLex) lexString(yylval *parserSymType, quoted bool) (int, bool) {
 
 		// If we hit a dollar sign, then check if we're starting
 		// another interpolation. If so, then we're done.
-		if c == '$' && x.peek() == '{' {
-			x.backup()
-			break
+		if c == '$' {
+			n := x.peek()
+
+			// If it is '{', then we're starting another interpolation
+			if n == '{' {
+				x.backup()
+				break
+			}
+
+			// If it is '$', then we're escaping a dollar sign
+			if n == '$' {
+				x.next()
+			}
 		}
 
 		if _, err := b.WriteRune(c); err != nil {

config/lang/lex_test.go

@@ -25,6 +25,16 @@ func TestLex(t *testing.T) {
 			[]int{STRING, PROGRAM_BRACKET_LEFT, IDENTIFIER, PROGRAM_BRACKET_RIGHT, lexEOF},
 		},
 
+		{
+			"foo $${bar}",
+			[]int{STRING, lexEOF},
+		},
+
+		{
+			"foo $$$${bar}",
+			[]int{STRING, lexEOF},
+		},
+
 		{
 			"foo ${\"bar\"}",
 			[]int{STRING, PROGRAM_BRACKET_LEFT, STRING, PROGRAM_BRACKET_RIGHT, lexEOF},