% perl -E 'system(q[opera http://www.perlmonks.org/]); say "hello!" '                                
hello!

##</code><code>##

% perl -E 'system(q[opera http://www.perlmonks.org/ &]); say "hello!" '
hello!

##</code><code>##

% perl -E '$r = fork; if($r == 0) { exec(q[opera http://www.perlmonks.org/]) } elsif(defined $r) { say "hello!" }'
hello!