I inspected the code and sorry it's not implemented.

In b $var $var is interpreted as a condition and the breakpoint is set at the current point in code.

Thats why you see something like this after listing breakpoints

  DB<105> L
  10:    };
   break if ($var)
[download]

you may wanna check cmd_b() on your own.

There is even no trace that it was even attempted to be implemented.

cmd_b_sub() explicitely ignores references.

Though I can find the anonymous sub in %DB::sub as

 "main::__ANON__[/tmp/tst.pl:10]" => "/tmp/tst.pl:6-10"

But I can't connect it to the subref.

... hmm wait ...

well DB::CvGV_name($mysubref) seems to fix it main::__ANON__[/tmp/tst.pl:10]

ok I will try to fix it, but this will result in a patch. (update see--> Re: how to set a breakpoint by a code reference (workaround))