accelerated stepping from a old thread and Perl changes.

[Rocky Bernstein]

I was looking at old debugger list postings on "accelerated stepping".

The general problem of how to make stepping feel right is a well trodden
topic. So let me describe how the trepanning debuggers such as
Devel::Trepan partially address this. The idea builds on something Kent
Sibilev added to ruby-debug, and as far as I know he was the first to do
this.

There is a setting called "set different" in ruby-debug (originally called
"set force") which can be "on" or "off". When "on" the setting causes
"next" and "step" commands to stop at a different line numbers for a given
frame. The stack frame is used because one wants to treat recursive calls
as "different". In the trepanning debuggers, I added "+" and "-" suffixes
to the "step" and "next" commands which over-ride the default setting.