use re 'debug';

##</code><code>##

2120 2140 2180 2197 2200 2203 2205 2234 2238 2259 2280 2299 2401

##</code><code>##

    s/\b(\d*)(\d\d) (?=\1\d\d\b)/$1$2_/g;
    s/ /\n/g;
    s/_/ /g;