#!/usr/sbin/dtrace -qs

dtrace:::BEGIN {
  depth = 0
}

perl$target:::sub-entry, perl$target:::sub-return
{
  depth += probename == "sub-entry" ? 0 : -1;

  printf("%*s %s %s\n", depth, "", probename == "sub-entry" ? "->" : "<-",
      copyinstr(arg0));
  depth += probename == "sub-entry" ? 1 : 0;
}