These are adapted from HerkForth.

    | 0=  |  n- | exit word if TOS = 0                                   |
    | <;  | nn- | exit word if NOS < TOS                                 |
    | >;  | nn- | exit word if NOS > TOS                                 |
    | <>; | nn- | exit word if NOS <> TOS                                |
    | if; |  f- | exit word if TOS is TRUE                               |
    | ?;  |  f- | exit word if TOS is TRUE. Leave Flag on stack if TRUE. |

~~~
:0=; n:zero? [ as{ 'popopodr i 'drdrre.. i }as ] if ;
:<;  lt? [ as{ 'popopodr i 'drdrre.. i }as ] if ;
:>;  gt? [ as{ 'popopodr i 'drdrre.. i }as ] if ;
:<>; -eq? [ as{ 'popopodr i 'drdrre.. i }as ] if ;
:if; [ as{ 'popopodr i 'drdrre.. i }as ] if ;
:?;  dup [ as{ 'popopodr i 'drdrre.. i }as ] if drop ;
~~~


```
:test (n-) n:even? if; 'Odd! s:put nl ;

#1 test
#2 test
```


```
nl '----------------- s:put nl
:test (n-) n:even? ?; 'Odd! s:put nl ;
#1 test dump-stack reset nl
#2 test dump-stack reset nl
```