The preferred and supported method of installing specific versions of formulae is to use the [Homebrew-versions](https://github.com/Homebrew/homebrew-versions) tap.
### Installing directly from pull-requests
You can browse pull requests https://github.com/Homebrew/homebrew/pulls
and install through the direct link. For example Python 3.3.0 pull request https://github.com/Homebrew/homebrew/pull/15199
Sometimes it's faster to download a file via means other than those strategies that are available as part of Homebrew. For example, Erlang provides a Torrent that'll let you download at 4–5× the normal HTTP method. Download the file and drop it in `~/Library/Caches/Homebrew`, but watch the file name. Homebrew downloads files as <code>{{ formula name }}-{{ version }}</code>. In the case of Erlang, this requires renaming the file from <code>otp_src_R13B03</code> to <code>erlang-R13B03</code>.
**New:**
```bash
mv the_tarball `brew --cache formula-name`
```
You can also pre-cache the download by using the command `brew fetch formula` which also displays the SHA1 and SHA256 values. This can be useful for updating formulae to new versions.
## Using Homebrew behind a proxy
Behind the scenes, Homebrew uses several commands for downloading files (e.g. curl, git, svn). Many of these tools can download via a proxy. It's a common (though not universal) convention for these command-line tools to observe getting the proxy parameters from environment variables (e.g. `http_proxy`). Unfortunately, most tools are inconsistent in their use of these environment parameters (e.g. curl supports `http_proxy`, `HTTPS_PROXY`, `FTP_PROXY`, `GOPHER_PROXY`, `ALL_PROXY`, `NO_PROXY`).
Luckily, for the majority of cases setting `http_proxy` is enough. You can set this environment variable in several ways (search on the internet for details), but the way I prefer is:
**NB:** this technique will also work if you prefer to use `sudo` with Homebrew. But as `sudo` clears the environment before executing Homebrew, your proxy settings may get lost.
This imports the brew environment into your existing shell, gem will pick up the environment variables and be able to build. As a bonus brew's automatically determined optimization flags are set.
## Install only a formula's dependencies (not the formula)