How to print value of a systemverilog class instance when a breakpoint is hit?

I would like to print "obj" or "obj.m_name" every time the following UVM code line is hit. What should I pass to the -exec switch to make this happen?

stop -create -line 308 -file $UVM_HOME/src/base/uvm_heartbeat.svh -all -exec {value obj}

The obvious attempt: "value obj",  produces an error:

ncsim: *E,PNOOBJ: Path element could not be found: obj.