When I try to write a file with some name for example `a` (then read it afterwards)

```
\usepackage{fancyvrb}

.........

\begin{VerbatimOut}{a}
file content here...
\end{VerbatimOut}

% process the file named a

```

I get a file not found error.

After debugging for a little I realize that `VerbatimOut` writes to a file named `a.tex` instead.

The package's documentation `fancyvrb-doc` only mention `VerbatimOut` in a single paragraph and no mention of this behavior.

How can I write to a file without extension? (using a different package is fine.)

---

I'm on an UNIX system so `a` and `a.` (empty extension) is different. Compiler is LuaLaTeX (`This is LuaHBTeX, Version 1.13.0 (TeX Live 2021/Arch Linux)`)