gnumake .RECIPEPREFIX problem

I am trying to use the special variable .RECIPEPREFIX in order to avoid the hard to see tabs, but it does not seem to work. 开发者_StackOverflowMy simple test makefile is:

    .RECIPEPREFIX = +

    all:
    + @echo OK

but I get the message:

xxx:4: *** missing separator.  Stop.

Which version of gnu make are you using? 3.81?

The .RECIPEPREFIX is only supported since 3.82. I've tested out your sample on 3.82 and it works.

http://cvs.savannah.gnu.org/viewvc/make/NEWS?revision=2.109&root=make&view=markup

• New special variable: .RECIPEPREFIX allows you to reset the recipe introduction character from the default (TAB) to something else. The first character of this variable value is the new recipe introduction character. If the variable is set to the empty string, TAB is used again. It can be set and reset at will; recipes will use the value active when they were first parsed. To detect this feature check the value of $(.RECIPEPREFIX).