overriding make install

In a Makefile.PL using ExtUtils::MakeMaker I wanted to completely
replace the make install method but
so far I have not succeeded.

When I added this:

sub MY::postamble {
	return <<'MAKE_FRAG';
install: Makefile
	echo "here"
MAKE_FRAG
}

I got the following error message:
Makefile:833: *** target file `install' has both : and :: entries.  Stop.

On the other hand when I had this:

sub MY:postamble {
	return <<'MAKE_FRAG';
install:: Makefile
	echo "here"
MAKE_FRAG
}

"make install" first did its regular installation procedure and then
called echo "here"
(though now that I tried it again I got "Invalid CODE attribute:
postamble at Makefile.PL line 9"
right when I tried to run perl Makefile.PL)

Is there a way to completely replace make install by my own code?

Gabor