To keep a record of all the (valid) guesses made, use an array:

my @guesses;

GUESS: ...
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Then, once a guess has been validated, push it onto the array:

push @guesses, $guess;
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When you want to print all the guesses made so far, you can say:

print join(', ', sort { $a <=> $b } @guesses), "\n";
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Hope that helps,