0F"><code>roll_left</code></font>' rolls the items to the left.
<p>
For example, the following shows how you might use `<font color="#82140F"><code>exch</code></font>' or
`<font color="#82140F"><code>roll_right</code></font>' to change the sense of a subtraction.
<p>
<TABLE SUMMARY="Example" BORDER="0" BGCOLOR="#efefef" WIDTH="100%">
<TR>
<TD>
<PRE>
<font color="#82140F">
show {rpn 1 2            -} " ... yields -1"
show {rpn 1 2 exch       -} " ... yields  1"
show {rpn 1 2 roll_right -} " ... yields  1"
</