## Local Constants: `{$let}`

Define local variables within the template scope:

Rust

```
let items = vec![("user", "User"), ("post", "Post")];

let code = ts_template! {
    {#for (key, class_name) in items}
        {$let upper = class_name.to_uppercase()}
        console.log("Processing @{upper}");
        const @{key} = new @{class_name}();
    {/for}
};
```

This is useful for computing derived values inside loops without cluttering the
Rust code.

## Mutable Variables: `{$let mut}`

When you need to modify a variable within the template (e.g., in a `while`
loop), use `{$let mut}`:

Rust

```
let code = ts_template! {
    {$let mut count = 0}
    {#for item in items}
        console.log("Item @{count}: @{item}");
        {$do count += 1}
    {/for}
    console.log("Total: @{count}");
};
```