matching.exs

defmodule Foo do
  def crash_unless_password(pw) do
    "password" = pw
    IO.puts "I didn't crash!"
  end

  def validate_v1(token) do
    case token do
      "tok_" <> _ ->
        IO.puts "Valid token `#{token}!`"
      _ ->
        IO.puts "Invalid token `#{token}, bruh.`"
    end
  end

  def validate_v2("tok_" <> _ = token), do: IO.puts "Valid token `#{token}!`"
  def validate_v2(token), do: IO.puts "Invalid token `#{token}, bruh.`"
end

IO.puts Foo.validate_v1 "tok_good"
IO.puts Foo.validate_v1 "bad"

IO.puts Foo.validate_v2 "tok_good"
IO.puts Foo.validate_v2 "bad"

Foo.crash_unless_password "password"
Foo.crash_unless_password "boof"

# $ elixir matching.exs
# Valid token `tok_good!`
# ok
# Invalid token `bad, bruh.`
# ok
# Valid token `tok_good!`
# ok
# Invalid token `bad, bruh.`
# ok
# I didn't crash!
# ** (MatchError) no match of right hand side value: "boof"
#     matching.exs:3: Foo.crash_unless_password/1
#     (elixir) lib/code.ex:370: Code.require_file/2