In those strings, you have exactly every other letter significant. If it's exactly every other letter, why not use that?
print pack C25, unpack n50, "DJduZsztX xADndoZtzhXexrD dPZezrXlx DhdaZ
+czkXexrD\n";
In that case, the filler letters don't need to be all DZX, so you can make the text slightly less readable:
print pack C25, unpack n50, " Jru scti eaentoethhue rt JPselrhlt ahcal
+chkeelrr\n";
Whereas, if you want to use only a few characters as filler, why not mix them more evenly instead of just alternating, as in?
$_="JZMzTustdrd z zrdMazpzindyzJd zez otzrhmieDNrmzzam".
"mznmd PmreZodymudmDrznzHmcmhrl haDtckeM".
"[dmZ]zur dmZ.\n"; s[[dmZ].][[dmZ]]siege; print;
(It is left as a homework for the reader to modify the above in such a way that it contains a few readable but irrelevant words in the string that are made up of mostly ignored characters.)
Ps. feel free to imagine all that join"|" and unpack"a" stuff was still in the japh, I just removed them to make the aspect I'm talking about clearer.