# Signature: # - Take 1 positional arg that is a Pair object that unpacks as: # - its key is a Str object; make it available in $desc variable # - its value is another Pair object; unpack it as: # - its key must be a UInt that's thruthy (so > 0), save it in var $plan # - its value must be a Callable object with signature that takes a # single Int positional argument; save that callable into variable &g # # Attempting to call this sub with any other type of argument is a typecheck # error, which can at times be checked even at compile-time. sub group( Pair ( Str :key($desc), Pair :value(( UInt :key($plan) where .so, :value( &g:(Int) )))) ) { dd [ $desc, $plan, g $plan ] } group 'foo' => 3 => -> Int $p { say "hi $p"; 42 } # OUTPUT: # hi 3 # ["foo", 3, 42]