Here is a list:

 - Item 1
 - Item 2 (Short explanation -- interjection -- more explaining)
 - Item 3
   - Sub-Item 1
   - Sub-Item 2

I want to convert to this:

Here is a list:

 * Item 1
 * Item 2 (Short explanation -- interjection -- more explaining)
 * Item 3
   * Sub-Item 1 
   * Sub-Item 2

As you can see, I want to keep hyphens that appear in words or sentences, but convert the hyphens that act as list-points into asterisks. 

's/(?!\b)-/\*/mg' almost works, but it adds asterisks where I don't want them, e.g.,:

 * Item 2 (Short explanation ** interjection ** more explaining) WRONG

Please help.