> For the complete documentation index, see [llms.txt](https://ploegert.gitbook.io/til/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://ploegert.gitbook.io/til/programmy/elixir/using-when-clauses-in-a-with-construct.md).

# Using When Clauses In A With Construct

Because Elixir's `with` construct supports the full power of the language's pattern matching, we can use `when` clauses to further narrow down our matches.

For instance, if we want to match against the response to an API request, but only for response status codes in the 2xx range, we can do something like the following:

```elixir
with %{status_code: code, body: body}
       when code >= 200 && code < 300 <- HTTPoison.get!(url),
     {:ok, decoded_body} <- Poison.decode(body) do
  {:ok, decoded_body}
end
```

See the [docs for `with`](https://hexdocs.pm/elixir/Kernel.SpecialForms.html#with/1) for more details.