With regard to things like this, I have learned (ahem... the hard way) to prefer “clear” over “clever.”

And to look through http://search.cpan.org before giving the slightest consideration for doing anything myself.   When I search for “IP address range” on that site, I am pointed to a slew of very-recent modules such as NetAddr::IP::Lite and mod:://Net::IP::RangeCompare.   Basically, when I see that, I think:   “okay, this problem is now basically solved.”

Sometimes you get burned by choosing to grab something recent out of CPAN and use it ... but those times are very rare, indeed.