In the version I have it looks like:

my @MonthDays = ( 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 );

...

    my $md = $MonthDays[$month];
        ++$md
            if $month == 1 && _is_leap_year( $year + 1900 );

        croak "Day '$mday' out of range 1..$md"  if $mday > $md or $md
+ay < 1;
        croak "Hour '$hour' out of range 0..23"  if $hour > 23  or $ho
+ur < 0;
        croak "Minute '$min' out of range 0..59" if $min > 59   or $mi
+n < 0;
        croak "Second '$sec' out of range 0..59" if $sec >= 60  or $se
+c < 0;
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