How to create a text spanner with a "half" arrow on right side

[Kate Sekula]

I am trying to create a text span solid line that ends with just 1/2 of an 
arrowhead on the right side.  Is there a way to set a graphic, something 
simple like ...

samplePath =
  #'((moveto 0 0)
     (lineto -1 -.5)
     (closepath))

... as the right text for the spanner?  Something like:

\once \override TextSpanner.bound-details.right.text = \samplePath