VARIABLE X
0 X !

"Change X from 0 to 3\n" TYPE
1 2 { 3 X ! } X PRESERVED
.S
"X: " TYPE X @ . EOL

DEPTH NDROP
EOL

"Change X from 4 to 7 and then QUIT\n" TYPE
4 X !
5 6 { 7 X ! QUIT } X PRESERVED
.S
"X: " TYPE X @ . EOL

DEPTH NDROP
EOL

"QUIT without changing X from 8\n" TYPE
8 X !
9 10 ' QUIT X PRESERVED
.S
"X: " TYPE X @ . EOL

DEPTH NDROP