for my $FQDN (@things){
   
    my $start_time = time_and_log($FQDN); 
  
    # do stuff with $FQDN
    
    time_and_log($FQDN, $start_time);
}

##</code><code>##

sub time_and_log {
    my $FQDN = shift;
    my $start = shift;

    if (! $start){
        # do start stuff
        $start = time;
        return $start;
    }
    else {
        # use $start for calculations,
        # then log
    }
}