Net::IP::LPM versions before 1.12 for Perl accept malformed prefix lengths.
Non-numeric and non-ASCII prefix lengths are accepted and treated as 0. Integers over 31 bits are silently truncated. A single malformed mask will poison the lookup table.
The result is that the lookup will silently succeed for every address. An allow-list will allow every address, and a deny-list will block every address.