Well, just chain a map-based solution like "mine" with the usual grep-based "uniq" or absorb the latter into the map():

my %saw;
my @parts = map { my $s=substr $str, $_, 3; 
                  $saw{$s}++ ? () : $s } 0..length($str)-3;

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In reply to Re^2: finding number of contiguous letters by blazar
in thread finding number of contiguous letters by Marknel

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