Cute idea, but the reverse of this line:
in reply to JAPH palindrome.
is not what you have written; it's this unfortunate thing:
print fi ('Just another Perl hacker,');
But the code you have does not rely on those parentheses being there, so you are safe.
;)',rekcah lreP rehtona tsuJ'( if tnirp
Also, you have no space in X__ATAD__, but you have a space in __DATA__ X. I guess the "plain-language" definition of a palindrome does ignore spaces. Presumably that can only make the task easier in Perl..