pattern-matching

# Basic matching
email = "user@example.com"
email =~ /@/  # => 4 (position of match)
email.match?(/@/)  # => true

# Capture groups

enum Status {
    Ok,
    Error(String),
    Pending,
}

use std::fmt;

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum OrderState {
    Pending,
    Paid,

#[derive(Debug, Clone)]
pub enum Outcome {
    Approve,
    Review,
    Reject(String),
}