Yes, surround the strings with parens to enforce list repetition ( vs string)

edit

  DB<126> @arr = (("A") x 2, ("T") x 2, ("C") x 3, ("G") x 3);
 => ("A", "A", "T", "T", "C", "C", "C", "G", "G", "G")
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update

see perlop#Multiplicative-Operators "repetition operator" for details

Binary "x" is the repetition operator. In scalar context or if the left operand is not enclosed in parentheses, it returns a string consisting of the left operand repeated the number of times specified by the right operand. In list context, if the left operand is enclosed in parentheses or is a list formed by "qw/STRING/", it repeats the list. If the right operand is zero or negative, it returns an empty string or an empty list, depending on the context.

but I have to admit it sounds confusing ... :)

update

hmm should maybe be rephrased:

  DB<129> $arr = ("G") x 3;
 => "GGG"
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always a string in scalar context!