Thing Selection

In a programming or markup language buffer, when pressed/clicked at
the start or end of a delimited thing (including lists, comments,
strings, arrays/vectors, sets, functions and markup pair tags in a
markup language), and not at the end of a line:
  ACTION KEY
     Marks the thing for editing.
  ASSIST KEY
     Marks and kills the thing for yanking elsewhere.

Note that the press must be on the first character of the delimiter of the thing.

There are also drag actions that work on delimited things. Delimited things include parenthesized lists, single and double quoted strings, bracketed arrays/vectors, sets with braces, programming language functions and markup pair tags (e.g. <div> </div> in HTML).

If no region is selected when the Action Mouse Key is dragged from a thing delimiter to another location, it copies the delimited thing to the release point of the drag. The release location may be in the same or a different buffer but if in the same buffer it must be outside of the delimited thing itself. Similarly, the Assist Mouse Key kills (cuts) the delimited thing at its original location and yanks (pastes) it at the new location.

The start of the drag must be on the first character of the starting or ending delimiter. For strings and comments, the drag must start on the first line of the thing.

Experiment with these drag actions and you will quickly find them easy to use and indispensable.