Question

I’m trying to parse an OID and extract the #18 but I am unsure on how to write it to count Right to Left using a dot as a delimiter:

1.3.6.1.2.1.31.1.1.1.18.10035

This regex will grab the last value

my $ifindex = ($_=~ /^.*[.]([^.]*)$/);

I haven’t found a way to tweak it to get the value I need yet.

Answer 1

What you need is simpler:

my $ifindex;

if (/(\d+)\.\d+$/)
{
   $ifindex = $1;
}

A couple of comments:

1. You don’t need to match the entire string, only the part you care about. Thus, no need to anchor to the beginning with ^ and use .*. Anchor to the end only.
2. [.] is a character class, intended for matching groups of characters. e.g., [abc] will match either a, b, or c. It should be avoided when matching a single character; just match that character instead. In this case you do need to escape it, since it is a special character: \..
3. I have assumed based on your example that all of the terms have to be numbers. Hence, I used \d+ for the terms.