Regular expression to recognize truncated search string forms?

I am trying to formulate a regex that recognizes a search term truncated by any number of characters on the right.

For example, if the search term is "pickle", the regular expression must recognize "pi", "pick", but not "pickaxe".

I originally came up with the following:

p(i(c(k(l(e)?)?)?)?)?

      

        
        
        
      

    

This works great, but it seems like a crude way to do it. Is there a better way to do this? I was looking for something similar to what I want, but I'm not really sure what to look for.