The output of system( ), exec( ), and open(PIPE,"|program") calls will not be sent to the browser unless Perl was configured with sfio. To learn if your version of Perl is sfio-enabled, look at the output of the perl -V command for the useperlio and d_sfio strings.
You can use backticks as a possible workaround:
print `command here`;
But this technique has very poor performance, since it forks a new process. See the discussion about forking in Chapter 10.