The let module adds a let directive to nginx that computes an expression
and assigns the result to a variable.  It understands arithmetic, string
concatenation and a set of functions, among them length, substr, hash and
the md5 and sha1 digests, so a value can be derived inside the
configuration instead of in an upstream.

This port only installs the module sources.  The module itself is built
by the nginx ports when their LET option is enabled.