If this is a module, then you can put something like this in your Makefile.PL (see here):

sub MY::postamble {
    return <<'MAKE_FRAG';
.PHONY: authorcover
authorcover: test
    cpanm Devel::Cover
    cover -test -coverage default,-pod
MAKE_FRAG
}
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Then all you need to do is e.g. perl Makefile.PL && make authorcover.