sub cheatemall {
   my $givetime = shift;
   my $curtime = time();
   my $oldalarm;
   my $oldsig = $SIG{ALRM};
   $SIG{ALRM} = die ( 'ALARM' );
   eval {
      $oldalarm = alarm( $givetime );
      alarm( $oldalarm ) if ( $oldalarm < $givetime );
      if ( ... ) { ## Apply your logic here.
          &reset_old_alarm( $curtime, $oldalarm );
          return ...;  ## return X
      } else {
          &reset_old_alarm( $curtime, $oldalarm );
          return ...;  ## return Y
      }
   };
   ## We must have died out to get here.
   if ( $@ =~ /OLD ALARM/ ) {
      ## We got caught on a parent alarm.  Re-create that
      ## alarm outside of our local eval block.
      kill( 'ALRM', $$);
   } elsif ( $@ =~ /ALARM/ ) {
      ## We alarmed out locally.
      return ...; ## return Y
   } else {
      ## Died for some other reason.. handle it here.
   }
}

sub reset_old_alarm {
   ## If you want to do object oriented stuff, you could 
   ## make this be sub DESTROY so that this logic happens
   ## whenever your watchdog object goes out of scope.
   my ($curtime, $oldalarm) = @_;
   return alarm(0) if ( $oldalarm == 0);
   $oldalarm -= ( time() - $curtime );
   die ( 'OLD ALARM' ) if ( $oldalarm <= 0 );
   alarm($oldalarm);  
}