hs: a pedestrian history search engine

HS searches the command history file for entries containing a specific pattern using the regular expression engine.
the results are displayed in the command window in the format:

#entry location: line

clicking the -location- will open the history file at this line;
clicking the -line- will copy/paste the line to the command prompt and may be return by an [ENTER] command.

see:

>> help hs

for more explanations for this snippet