DB<1>h
T               Stack trace.
s [expr]        Single step [in expr].
n [expr]        Next, steps over subroutine calls [in expr].
<CR>            Repeat last n or s command.
r               Return from current subroutine.
c [line|sub]    Continue; optionally inserts a one-time-only breakpoint
                at the specified position.
l min+incr      List incr+1 lines starting at min.
l min-max       List lines min through max.
l line          List single line.
l subname       List first window of lines from subroutine.
l $var          List first window of lines from subroutine referenced by $var.
l               List next window of lines.
-               List previous window of lines.
w [line]        List window around line.
.               Return to the executed line.