viper-mouse-search-key

viper-mouse-search-key is a variable defined in `viper-mous.el'.
Its value is

(meta shift 1)

Documentation:
Key used to click-search in Viper.
This must be a list that specifies the mouse button and modifiers.
The supported modifiers are `meta', `shift', and `control'.
For instance, `(meta shift 1)' means that holding the meta and shift
keys down and clicking on a word with mouse button 1
will search for that word in the buffer that was current before the click.
This buffer may be different from the one where the click occurred.

You can customize this variable.