include search path doesn't include $(prefix)/include?

[Steve Byan]

The gnu make manual states that make will search the prefix/include 
directory as part of the search path for the include directive, where 
"prefix" is in italics. I interpreted this to mean that the value of 
the variable "prefix" is substituted for the italicized "prefix", and 
the resulting path becomes part of the search path.

However, I'm clearly wrong, because the following makefile snippet 
results in make complaining that the include file can't be found:

prefix = $(EGEN_BUILD_ROOT)/eng_tools/share
include startup.mk

while this works fine:

prefix = $(EGEN_BUILD_ROOT)/eng_tools/share
include $(prefix)/include/startup.mk

Would someone please explain what the make manual is trying to say 
about "prefix/include"? Thanks.

Regards,
-Steve
--------
Steve Byan <address@hidden>
Software Architect
Egenera, Inc.
165 Forest Street
Marlboro, MA 01752
(508) 858-3125