For example, with this dnssec-policy.conf:

################################################################################
## Do not edit this file, it is autogenerated, edit dnssec-policy.conf.proto  ##
################################################################################
policy default-dnssec {
        directory "/etc/namedb/keys";
        algorithm rsasha512;
        key-size zsk 1024;
        key-size ksk 2048;
        pre-publish zsk 2w;
        post-publish zsk 2w;
        roll-period zsk 2mo;
        roll-period ksk 0;
        coverage 6mo;
};

algorithm-policy RSASHA1 {
        post-publish zsk 2w;
        pre-publish zsk 2w;
        roll-period zsk 2mo;
        roll-period ksk 0;
        coverage 6mo;
};

zone 99example.com {
        policy default-dnssec;
};

Output when run:
# dnssec-keymgr
/usr/local/etc/namedb/dnssec-policy.conf:23:syntax error near '99'


... never exits. 

Domains beginning with numbers do exist, hence the script should be able to work with them.