concerned with hacking the low-level innards of perl

-d:*foo=bar,baz*
     runs the program under the control of a debugging, profiling, or
     tracing module installed as Devel::foo. E.g., -d:DProf executes the
     program using the Devel::DProf profiler. As with the -M flag,
     options may be passed to the Devel::foo package where they will be
     received and interpreted by the Devel::foo::import routine. The
     comma-separated list of options must follow a "=" character. See
     perldebug.