([0-9]?\d\d?|2[0-4]\d|25[0-5])

##</code><code>##

(1?\d\d?|2[0-4]\d|25[0-5])

##</code><code>##

perl -nle 'print if s/((1?\d\d?|2[0-4]\d|25[0-5])\.){3}(?=\d+)/xxx.xxx.xxx./g'