pm.syntax

# case version
case expr
in pat [if|unless cond]
  ...
in pat [if|unless cond]
  ...
else
  ...
end

pat: var                                                   # Variable pattern. It matches any value, and binds the variable name to that value.
   | literal                                               # Value pattern. The pattern matches an object such that pattern === object.
   | Constant                                              # Ditto.
   | var_                                                  # Ditto. It is equivalent to pin operator in Elixir.
   | (pat, ..., *var, pat, ..., id:, id: pat, ..., **var)  # Deconstructing pattern. See below for more details.
   | pat(pat, ...)                                         # Ditto. Syntactic sugar of (pat, pat, ...).
   | pat, ...                                              # Ditto. You can omit the parenthesis (top-level only). 
   | pat | pat | ...                                       # Alternative pattern. The pattern matches if any of pats match.
   | pat => var                                            # As pattern. Bind the variable to the value if pat match.

# one-liner version
$(pat, ...) = expr                                         # Deconstructing pattern.