[perl #123808] [BUG] qqw{} and << >> behaviour doesn't match

[via RT]

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It seems that although qqw{} and << >> are equivalent

my $a = 42;
<<$a b c>>.perl;      # ("42", "b", "c")
qqw{$a b c}.perl;     # ("42", "b", "c")

they don't always behave the same.  For instance:

my $a = 42; say <<$a b c>>;   # 42bc
my $a = 42; say qqw{$a b c};  # 42 b c

moritz++ used this on IRC:
sub f(*@a) { say @a.elems }; my $a = 42; f «$a b c»; f qqw{$a b c}
OUTPUT«3␤3␤»

multi f(*@a) { say @a.elems }; multi f($one) { say 'one'}; f «b c»; f qqw{b c}
OUTPUT«2␤one␤»

and showed that the quoting constructs differ when there is a single-element 
multi candidate available.

One would expect that these two constructs should behave in the same manner.