perl -e '@stack = (); sub notify { return qq~!!!!@_[0]!!!~}; for(qw~+ - + - + - + + - +~) {push @stack, $_; (@stack[-2] ne $_  )? print 0 : print notify(1)   };'

##</code><code>##

 perl -e '@stack = (); sub notify { return qq~!!!!@_[0]!!!~}; for(qw~+ - + - + - + + - +~) {push @stack, $_; (@stack[-2] ne $_  )? print 0 : print notify(1); if (@stack >= 3){shift @stack}   };  use Data::Dumper; print Dumper \@stack;'

##</code><code>##

0000000!!!!1!!!00$VAR1 = [
          '-',
          '+'
        ];