support define variable start with '$'

src/components/inspector.tsx

@@ -338,7 +338,7 @@ const TreeInspector: FC = () => {
                       rules={[
                         {
                           validator(_, value: VarItem) {
-                            if (!value.name || !/^[_\w]+\w*$/.test(value.name)) {
+                            if (!value.name || !isValidVariableName(value.name)) {
                               return Promise.reject(new Error(t("tree.vars.invalidName")));
                             }
                             if (!value.desc) {

src/misc/b3util.ts

@@ -141,7 +141,7 @@ export const isNewVersion = (version: string) => {
 };
 
 export const isValidVariableName = (name: string) => {
-  return /^[a-zA-Z_$]*$/.test(name);
+  return /^[a-zA-Z_$][a-zA-Z_$0-9]*$/.test(name);
 };
 
 export const isSubtreeRoot = (data: NodeData) => {