Status of user-settable breakpoints, or breakpoint number NUMBER.
The "Type" column indicates one of:
[tab]
breakpoint - normal breakpoint
[tab]
watchpoint - watchpoint
The "Disp" column contains one of "keep", "del", or "dis" to indicate
the disposition of the breakpoint after it gets hit. "dis" means that the
breakpoint will be disabled. The "Address" and "What" columns indicate the
address and file/line number respectively.
Convenience variable "$_" and default examine address for "x"
are set to the address of the last breakpoint listed unless the command
is prefixed with "server ".
Convenience variable "$bpnum" contains the number of the last
breakpoint set.