I doubt that anything beyond the core Perl functions will be needed:

my $birthday = "2/29/1980"; # (not really -- just an example)
my ($month,$date) = split /\//, $birthday;

my ($today,$thismonth) = (localtime)[3,4];
$thismonth++; # localtime gives you "0" for January

&letsParty if ( $today == $date and $thismonth == $month );
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Do read the output of "perldoc -f localtime" -- a great read.