use strict;
use warnings;
use Time::Piece;

my $ctime = Time::Piece->new;
my $oldtime = Time::Piece->strptime('Dec 19 17:01:00 2016', '%b %d %T %Y');

print "The current time is $ctime\n";
print "The old time is $oldtime\n";

my $halfago = $ctime - 1800;

print "Half an hour ago is $halfago\n";

if ($oldtime > $halfago)
{
	print "Old time is within a half hour\n";
}
else
{
	print "Old time is outside a half hour\n";
}

##</code><code>##

The current time is Mon Dec 19 17:07:06 2016
The old time is Mon Dec 19 17:01:00 2016
Half an hour ago is Mon Dec 19 16:37:06 2016
Old time is outside a half hour