$@, the current target
$< the first pre-requisite
$^ all the pre-requisites
$* the prefix shared by target and dependent files

# Shell invocation
VAR= $(shell pwd)

# printing warnings
$(warn Warning: foo!) and $(error foo)

# Invoking the same make as yourself
@make

# functions
define say
	@echo "Curent value of \$\@ is $@\n"
endef
blah:
	$(say)

# Targets that don't produce a file.
.PHONY: clean
clean:
	rm *.o temp

# stuff 
$(subst search,replace,$@)
$(addprefix -I,$(include_dirs))