Consider reading perlintro, perlop, and perldata for a better understanding of creating lists, populating arrays, and using quote-like constructs. If ":", "$string\n", and "$string2\n" create strings, then "1,2,3,4,5" must also do so. And therefore if double quotes are used for creating strings, the double-quote operator must NOT be for creating lists. You instead wanted:

my @input = (1, 2, 3, 4, 5);
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