Success: [eclipse]: [user]. go :- getval(i,2) -> exit_block(h). user compiled 100 bytes in 0.02 seconds yes. % write 'hello' if global variable i is 2. [eclipse]: setval(i,1), block(go, h, write(hello)). no. [eclipse]: setval(i,2), block(go, h, write(hello)). hello yes. Error: exit_block("a"). (Error 5). exit_block(a). (Error 230).