You should probably be using system instead of exec. Remember that exec actually converts the currently running process into the given command, which might not work as well in a http-process environment.

open(X10, "$command|");
print join('', <X10>);
close(X10);

# Or

print `$command`
[download]

Unless you are getting an error, in which case you may want to use CGI::Carp.