=head1 BUGS

Builtin functions cannot be measured by Devel::DProf.

With a newer Perl DProf relies on the fact that the numeric slot of
$DB::sub contains an address of a subroutine.  Excessive manipulation
of this variable may overwrite this slot, as in

  $DB::sub = 'current_sub';
  ...
  $addr = $DB::sub + 0;

will set this numeric slot to numeric value of the string
C<current_sub>, i.e., to C<0>.  This will cause a segfault on the exit
from this subroutine.  Note that the first assignment above does not
change the numeric slot (it will I<mark> it as invalid, but will not
write over it).