if ($x < 0.5) {
   # All is ok
   $ok = 1;
   ... normal operation mode ...
}
elsif ($x > 0.7) {
   # Things are definitely bad.
   $ok = 0;
   ... exceptional operation mode ...
}
elsif ($ok) {
   # In deadband. Was last ok.
   ... normal operation mode ...
}
else {
   # In deadband. Was last bad.
   ... exceptional operation mode ...
}