Pattern matching lets you branch on values and variants with a sequence of `case` arms. It is useful both in ordinary control flow and in error recovery.
## Match a value directly
Use `match` when you want to inspect one value and choose a result from several cases. Literal patterns match exact values, and `_` acts as the fallback arm.
```tea
const status = 200
const label = match status
case 200 => "ok"
case 404 => "not found"
case _ => "unexpected"
end
@println(label)
```
## Pattern matching in error recovery
Pattern matching is especially useful in `catch` blocks, where `case is ...` lets you branch on specific error variants and recover with different values.
```tea
error DataError {
Missing(path: String)
Permission
}
def describe(path: String) -> String
try read(path) catch err
case is DataError.Missing
`missing:${err.path}`
case is DataError.Permission
"denied"
case _
"unexpected"
end
end
```
- Use literal patterns such as `case 200` for exact values.
- Use `case is Type.Variant` to match specific typed variants.
- Use `_` as the final fallback when no earlier pattern matches.