enterblock
enterblock(fs, &bl, 0);
enterblock(fs, &bl, 1);
enterblock(fs, &bl1, 1); /* loop block */
enterblock(fs, &bl2, 0); /* scope block */
enterblock(fs, &bl, 0); /* scope for declared variables */
enterblock(fs, &bl, 1); /* scope for loop and control variables */
enterblock(fs, &bl, 0); /* must enter block before 'goto' */
enterblock(fs, &bl, 0);
enterblock(fs, bl, 0);