$_ = "aabbccdd";
if ( /^(\w\w)\w\w(\w\w)\w\w$/ ) {
    if ( /^\w\w(\w\w)\w\w(\w\w)$/ ) {
        print "inner: $1 $2\n";
    }
    print "mid: $1 $2\n"; # the inner if's vars are still accessible here
}
print "outer: $1 $2\n";