What does %~dp0 mean, and how does it work?

Question

I find %~dp0 very useful, and I use it a lot to make my batch files more portable.

But the label itself seems very cryptic to me... What is the ~<

Answer 1

Great example from Strawberry Perl's portable shell launcher:

set drive=%~dp0
set drivep=%drive%
if #%drive:~-1%# == #\# set drivep=%drive:~0,-1%

set PATH=%drivep%\perl\site\bin;%drivep%\perl\bin;%drivep%\c\bin;%PATH%

not sure what the negative 1's doing there myself, but it works a treat!