Cryptic idiom

[Frédéric Fauberteau <triaxx%netbsd.org@localhost>]

Hi,

I am not sur to understand this idiom in mk/tools/replace.mk:

```
.  elif defined(TOOLS_PLATFORM.${_t_}) && !empty(TOOLS_PLATFORM.${_t_})
#####
##### For each system-supplied tool, break the tool down into a path
##### and arguments so that either a symlink or a wrapper will be
##### properly created.
#####
TOOLS_CREATE+=    ${_t_}
TOOLS_PATH.${_t_}?= \
  ${TOOLS_PLATFORM.${_t_}:C/^/_asdf_/1:M_asdf_*:S/^_asdf_//}
TOOLS_ARGS.${_t_}?= \
  ${TOOLS_PLATFORM.${_t_}:C/^/_asdf_/1:N_asdf_*}
.  endif
```

Given that TOOLS_PLATFORM.${_t_} is defined and not empty, how could applying ":C/^/_asdf_/1:M_asdf_*:S/^_asdf_//" produce anything other than TOOLS_PLATFORM.${_t_} itself?