You need to convert the date to something that can be compared. Epoch might be a good choice.
Dates are always a bit tricky to deal with (time zones, daylight saving, ...) but if you know your format you can use something like the following as a starting point
use strict;
use warnings;
use Time::Local;
while (<DATA>) {
if (/FIND/) {
my $now = time;
my ($month, $day, $year, $hours, $minutes, $seconds, $AMPM) =
+split /\/| |:/;
$hours += 12 if $AMPM eq 'PM';
my $time = timegm($seconds, $minutes, $hours, $day, $month-1,
+$year-1900);
print "within 30 mins" if $now - $time < 30*60;
}
}
__DATA__
7/21/2009 5:47:29 PM:> DATA
7/21/2009 5:48:49 PM:> DATA1
7/21/2009 5:49:20 PM:> FIND
7/28/2009 9:49:20 AM:> FIND
7/21/2009 5:50:39 PM:> DATA3
7/21/2009 5:51:29 PM:> DATA4
7/21/2009 5:52:59 PM:> DATA5
7/21/2009 5:53:19 PM:> DATA6
cheers, si_lence