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# Pattern Matching

## Pattern Matching

Variables are bound to values through the _pattern matching_ mechanism. Pattern
matching occurs when evaluating the `case`, `receive`, `try`, and
the match operator (`=`) expressions.

In pattern matching, a left-hand side [pattern](expressions.md#patterns) is
matched against a right-hand side [term](expressions.md#terms). If the matching
succeeds, any unbound variables in the pattern become bound. If the matching
fails, an exception is raised.

_Examples:_

```erlang
1> X.
** 1:1: variable 'X' is unbound **
2> X = 2.
2
3> X + 1.
3
4> {X, Y} = {1, 2}.
** exception error: no match of right hand side value {1,2}
5> {X, Y} = {2, 3}.
{2,3}
6> Y.
3
```