It would be nice if there were functions that allowed us to validate strings as being IPv4 or IPv6 addresses for example isvalidip( "ipv4", "220.127.116.11" ), isvalidip( "ipv6", "FE80:CD00:0000:0CDE:1257:0000:211E:729C"). This is most useful in validating policy driven by data that comes from external systems.
This capability should exist already as part of functions like isipinsubnet(). It's possible to do this validation from policy, but it could be easier.
For example, this policy from Ted Zlatanov will validate ipv4 addresses.