Feature request: Equivalent of glue for capitalization, a/an

[Sorry to muck this place up by creating so many tickets all at once!]

I was wondering if there was an equivalent of glue for capitalization or for a/an. Examples:

```
{~{~why|well|}, |}hello there!
```

Could evaluate to

```
Why, hello there!
Well, hello there!
Hello there!
```

The same idea could work for a/an:

```
=== function syn_completely ===
{~completely|totally|absolutely}

=== knot ===
It's {syn_completely()} beautiful day, is it not?
```

```
It's a completely beautiful day, is it not?
It's an absolutely beautiful day, is it not?
It's a totally beautiful day, is it not?
```