GNU make manual 翻译( 一百五十一)

   To use the canned sequence, substitute the variable into the recipe
of a rule.  You can substitute it like any other variable (*note Basics
of Variable References: Reference.).  Because variables defined by
`define' are recursively expanded variables, all the variable
references you wrote inside the `define' are expanded now.  For example:

     foo.c : foo.y
             $(run-yacc)

`foo.y' will be substituted for the variable `$^' when it occurs in
`run-yacc''s value, and `foo.c' for `$@'.

   This is a realistic example, but this particular one is not needed in
practice because `make' has an implicit rule to figure out these
commands based on the file names involved (*note Using Implicit Rules:
Implicit Rules.).

   In recipe execution, each line of a canned sequence is treated just
as if the line appeared on its own in the rule, preceded by a tab.  In
particular, `make' invokes a separate subshell for each line.  You can
use the special prefix characters that affect command lines (`@', `-',
and `+') on each line of a canned sequence.  *Note Writing Recipes in
Rules: Recipes.  For example, using this canned sequence:

     define frobnicate =
     @echo "frobnicating target $@"
     frob-step-1 $< -o $@-step-1
     frob-step-2 $@-step-1 -o $@
     endef

`make' will not echo the first line, the `echo' command.  But it _will_
echo the following two recipe lines.

   On the other hand, prefix characters on the recipe line that refers
to a canned sequence apply to every line in the sequence.  So the rule:

     frob.out: frob.in
             @$(frobnicate)

does not echo _any_ recipe lines.  (*Note Recipe Echoing: Echoing, for
a full explanation of `@'.)