Filtering ${.VARIABLES} ?

[Frazer Worley]

I want a target which just dumps the variables defined in my Makefile. So I wrote this - using ${.VARIABLES} and
filtering using origin.

VERBOSITY=                BRIEF
PROJECT_TAG=              btc

define dump_variable
endef

dumpvars:
  $(foreach i,${.VARIABLES},\
    $(if $(filter file,$(origin $i)),\
      $(info $i),\
    )\
  )

Problem is though - that it reports "dump_variable" also ... which is a user defined macro
rather than a simple variable.

This becomes an issue when I extend dumpvars to report the value of the variables its reporting,
I get Make errors when dumpvars issues $(info $i = $($i)) on some of my macros.

So I'd like to filter out all macros and just report the variables. I've tried using a $(filter ...) based
on the variable name - macros are always lowercase named - but the filter doesn't seem to support
regexps. .... so that doesn't work.

Any tips much appreciated.

Thanks,

-Frazer