The colon means a named variable, *not* a Pair

Specifying a Pair would be a Positional, and thus not match the signature.

doc/Language/5to6-nutshell.pod6

@@ -622,7 +622,7 @@ sub get_the_loot( $loot, *%options ) { # The * means to slurp everything
 get_the_loot( 'diamonds', quiet_level => 'very', quantity => 9 ); # Note: no curly braces in this API
 
 # Perl 6, API changed to specify valid options
-# The colon before the sigils means to expect a Pair,
+# The colon before the sigils means to expect a named variable,
 # with the key having the same name as the variable.
 sub get_the_loot( $loot, :$quiet_level?, :$quantity = 1 ) {
     # This version will check for unexpected arguments!