I tried assigning two different shortcuts to inserting powers of ten: 

```
command-sequence math-insert 10^{ }; up;
math-insert 10^{ }

```

However, if I select some text and then use one of the shortcuts, the selected text is *replaced* instead of being used as the superscript content.

In contrast, a "system-defined" `math-insert` command such as `math-insert \hat` does work both ways: if nothing is selected, a hat is inserted and the cursor is placed under the hat; if any text is selected, it is moved under the hat.

How can I make use of selected text when creating custom commands and command sequences?

EDIT: Curiously, this underbrace sequence works too

```
command-sequence math-insert \underbrace; char-forward; math-subscript;

```

unlike the power-of-ten example.