im lazy. straight from copilot :)

🔑 Pattern Matching with String Keys
By default, Ruby’s hash pattern matching expects symbol keys. That’s why your example works when you load YAML with symbolize_names: true. If you keep string keys, you need to explicitly match them:

ruby
y = YAML.safe_load(yaml_data) # no symbolize_names

y["cards_on_hand"].each do |a_card|
  case a_card
  in { "suite" => String => captured_suite, "value" => "king" }
    puts "you have a king on your hand and its suite is #{captured_suite}"
  else
    puts "a card of no interest #{a_card.inspect}"
  end
end
Notice the difference:

suite: → matches a symbol key

"suite" => → matches a string key

So:

Use symbolize_names: true if you want to work with symbols.

Or match with "key" => if you want to keep string keys.

📦 Passing Patterns into Functions
Patterns in Ruby are objects (they’re part of the language syntax). You can’t directly “store” a pattern as a variable, but you can wrap matching logic in a method and use case ... in inside it.

Example:

ruby
def match_card(card, pattern)
  case card
  in pattern
    yield $~ if block_given? # or just return true
  else
    nil
  end
end

pattern = { suite: String => suite, value: "king" }

y[:cards_on_hand].each do |card|
  match_card(card, pattern) do
    puts "Captured suite: #{suite}"
  end
end
Another approach is to use procs/lambdas for reusable matching logic:

ruby
king_pattern = ->(card) {
  case card
  in { suite: String => s, value: "king" }
    s
  else
    nil
  end
}

y[:cards_on_hand].each do |card|
  if (suite = king_pattern.call(card))
    puts "You have a king of #{suite}"
  end
end
This way, you can pass around reusable matchers like any other object.

🚀 Key Takeaways
Use symbol: for symbol keys, "string" => for string keys.

Wrap patterns in methods or lambdas to pass them around.

Captures (=> var) work fine inside those reusable matchers.