s[(?:\G|^)((?:$char){1,$len}(?:$eseq)*)\s][$1\n]gm;
    #    ^^^^                                        ^
    #    vv
    s[(?:\G|(?<=\s))((?:$nonsp){$len}(?:$eseq)*)(?=[^$esc\s])][$1\n]g;