sub MY::post_constants {
    # With this, you can override INSTALLSITELIB when
    # you call WriteMakefile, or when you run make.
    # You can also override INSTALL_DB_FILE when you
    # run make. Assume you've set @list_of_db_files
    join("\n",
         'INSTALL_DB_FILES=\$(INSTALLSITELIB)/db',
         "DB_FILES=@list_of_db_files");
}

sub MY::postamble {
    my $self = shift;

    my @text;
    push(@text,
         'install:: install.dbfiles',
         '',
         'install.dbfiles:: $(DB_FILES)',
         "\t\$(MKPATH) \$(INSTALL_DB_FILES)",
         "\t\$(CP) \$(DB_FILES) \$(INSTALL_DB_FILES)");

    join("\n", @text);
}