[perl #122917] [UsingPerl6-draft.pdf ] unpacking example can not run

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UsingPerl6-draft.pdf 
page 47
 4.8 Unpacking


code:
sub first-is-largest(@a){
        my :($first, *@rest ) := \(|@a)
        return $first >= all(@rest);
}



can not run ,error message:
===SORRY!=== Error while compiling unpacking.p6
Malformed my
at unpacking.p6:4
------>         my ⏏:($first, *@rest ) := \(|@a)
    expecting any of:
        scoped declarator



perl6 --version
This is perl6 version 2014.09 built on MoarVM version 2014.09