use strict;
use Time::Hires qw (usleep);
my $start = foo
my $stop = bar
while () {
        my $now           = ParseDate("now");
       
        if ( Date_Cmp( $start, $now ) == 0 ) {
            
            start_application;
        }

        if ( Date_Cmp( $stop, $now ) <= 0 ) {
            stop_application;
            last;
        }
        usleep(800000);

    }