use B;

my $subref = sub {
  # some subroutine
}

my $b = B::svref_2object( $subref );
my $op = $b->START;

do {
  print B::class($op) . " : " . $op->name . " (" . $op->desc . ")\n";
} while $op = $op->next and not $op->isa("B::NULL");