perl, append a character to i-th capturing group

Question

I have this one liner:

perl -pe 's|.*?((\d{1,3}\.){3})xxx.*|\1|'

I feed this command with some input, like 192.168.1.xxx, and it works. Now, I want to append a 0 to the output sequence, but of course if I just append the 0 right after the \1 it will be parsed as the tenth capturing group. How can I concatenate then it to the \1 directive?

Answer 1

You should use $1 instead of \1 in substitutions. Then you can use braces to write it unambiguously like this:

perl -pe 's|.*?((\d{1,3}\.){3})xxx.*|${1}0|'