use CGI ':standard';

my $pid = fork;
if ($pid == 0) {                    # we are the child
  close;  # close all filehandles so server won't try to stay open
  exec 'backupprogram' or exit  ;  # transfer execution
}
elsif ($pid) {                      # we are the original process
  print header, start_html, 
    'Backup initiated. You can close this window at any time', 
    end_html;
}
else { die "Fork failed: $!\n"; }   # something went wrong