There are a couple ways to do this. The best that comes to mind is to grab a module for it (I prefer Date::Calc personally). You could then do something like

unless(check_date(param('year'), param('month'), param('day')) {
   # do something
}
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A non-modular way to accomplish this would be to create an array of month lengths, i.e.

my @month_lengths = (31, 28, 31, 30, ......);
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which would require one additional check for leap-year.