${PYTHON_CMD}/${PERL} in _CONFIGURE_WITH not working

[Jason Unovitch]

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Hello,
I seem to be missing something simple found while converting
net-mgmt/collectd5 over to option helpers.  I've been using the
following Makefile entries.

PERL_USES=                      perl5
PERL_CONFIGURE_ENABLE=          perl
PERL_CONFIGURE_WITH=            perl=${PERL} perl-bindings
PYTHON_USES=                    python:2
PYTHON_CONFIGURE_ENABLE=        python
PYTHON_CONFIGURE_WITH=          python=${PYTHON_CMD}

Everything looks good for the _WITH variables.  The correct variable
expansion appears to be taking place:

% make -VPERL_CONFIGURE_WITH                                                             
perl=/usr/local/bin/perl perl-bindings
% make -VPYTHON_CONFIGURE_WITH                                                           
python=/usr/local/bin/python2.7

However, for CONFIGURE_ARGS the ${PERL} and ${PYTHON_CMD} variables are
getting swallowed up.  The port will fail to compile because of this.

% make -VCONFIGURE_ARGS
"--enable-python --with-python= "
"--enable-perl --with-perl= --with-perl-bindings"

Any ideas or suggestions on where to look for this?  Thanks!
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