INITIAL_STATE  SOME_STATE     FINAL_STATE
         +-----+        +-----+        +-----+
start--->|     |---+--->|     |------->|     |--->accept
         +-----+   |    +-----+        +-----+
                   |       |
                   +-------+

##</code><code>##

INITIAL_STATE: {
   ...
   goto SOME_STATE;
}

SOME_STATE: {
   ...
   if ( ... ) {
      goto SOME_STATE;
   } else {
      goto FINAL_STATE;
   }
}

FINAL_STATE: {
   ...
}

##</code><code>##

sub initial_state {
   ...
   return some_state();
}

sub some_state {
   ...
   if ( ... ) {
      return some_state();
   } else {
      return final_state()
   }
}

sub final_state {
   ...
   return;
}

initial_state();

##</code><code>##

sub initial_state {
   ...
   goto &some_state;
}

sub some_state {
   ...
   if ( ... ) {
      goto &some_state;
   } else {
      goto &final_state;
   }
}

sub final_state {
   ...
   return;
}

initial_state();

##</code><code>##

sub initial_state {
   ...
   return \&some_state;
}

sub some_state {
   ...
   if ( ... ) {
      return \&some_state;
   } else {
      return \&final_state;
   }
}

sub final_state {
   ...
   return undef;
}

my $state = \&initial_state;
while ( $state ) {
   $state = $state->();
}