TIMTOWTDI of course, but syntax updates to gather since the OP allow you to write it as: 

my @in = <a a a a b c c a a d e e e e>;
say gather for @in -> $i {
    state $last;
    $last = take $i if $i ne $last;
};

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In reply to Re^3: 99 Problems in Perl6 by gaal
in thread 99 Problems in Perl6 by Ovid

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