sub that_cgi_script {
  ...
  eval { do_something() };
  ...
}
sub do_something {
  # 1) may return if everything ok
  # 2) may die on error, but such error non-important to
  #    calling code in above case and will be catched by
  #    eval and ignored
  # 3) may redirect: print Location header and call exit()
}