People cannot answer you question because we don't have the exact data that you are a working with. You gave an example, but we can never be sure if you just typed it in correctly and just missed the reason behind it not working.

An alternative solution, why don't you split the data,

my ($month_abbrev, $day, $year) = split qr{\s+}, $data, 3;
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This should give you the same information but is easier to understand and should be little faster than a regexp.