Immutable values and pattern matching

The idea

Enter with basic functions and collections understood. In Elixir, = is a match operator: it succeeds when the value on the right fits the pattern on the left. A variable in a pattern can receive a binding, and tuple patterns can extract several related pieces at once. A mismatched shape raises an error instead of silently inventing missing data.

Values are immutable. Rebinding a variable name makes that name refer to another value; it does not alter the previous value or other bindings referring to it. The pin operator ^ asks a pattern to match an existing variable’s value instead of rebinding that variable. This distinction matters in parsing, function clauses, and message handling, where a familiar name alone may not express an equality check.

{:ok, count} = {:ok, 5}
old = count
count = count + 2
IO.inspect({old, count})

{5, 7}

The tuple match binds count to five. Rebinding count later leaves the value associated with old unchanged.