None of the $ vars have it but you can find it with something like this:

perl -le'chomp($h=`hostname`);print +(join ".",unpack('C4', gethostbyname $h))'

or in you code you can expand it out something like:

chomp(my $host=`hostname`);
my @address=unpack('C4', gethostbyname $host);
print "ip address is " . (join ".", @address);

I am sure this can be a lot tidier. Of course on some hosts you may have multiple interfaces to worry about.

Cheers.