my @string = qw(a a a a b b b c d e f q q q r r r);
my @singletons = uniq(@string);
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where @singletons is a list of the elements in @string which occur only once.

This is not true, uniq removes duplicates from an array. From the doc:

uniq LIST
Returns a new list by stripping duplicate values in
LIST. The order of elements in the returned list is
the same as in LIST. In scalar context, returns the
number of unique elements in LIST.

my @x = uniq 1, 1, 2, 2, 3, 5, 3, 4; # returns 1 2 3 5 4
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