print fi ('Just another Perl hacker,');
[download]

;)',rekcah lreP rehtona tsuJ'( if tnirp
[download]

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..

Thanks, I didn't notice the inverted parenthesis, obviously. That's what I get for checking manually. I also didn't realize, as this script evolved, that I no longer had use for the parenthesis at all. At one point, adding them was necessary for a successful compile.

Yes, I went with the rule that whitespace and newlines did not have to match.

Now, trying to create a JAPH palindrome without the use of comments or DATA?

;;print "Just another Perl hacker";s;"rekcah lreP rehtona tsuJ" tnirp;
+;
[download]

Extended to use the shebang line:

#!/usr/bin/perl  -- !m
;;;print "Just another Perl hacker";
s
;"rekcah lreP rehtona tsuJ" tnirp;;;
m! --  lrep/nib/rsu/!#
[download]

That truly is awesome looking, but it isn't working on my Perl 5.10

jbm@Foucault:~/Code/perl
$ ./javafan.pl 
Can't open perl script "!m": No such file or directory
jbm@Foucault:~/Code/perl
$ perl -v

This is perl, v5.10.0 built for darwin-thread-multi-2level
(with 2 registered patches, see perl -V for more detail)

jbm@Foucault:~/Code/perl
$ cat javafan.pl 
#!/usr/bin/perl  -- !m
;;;print "Just another Perl hacker";
s
;"rekcah lreP rehtona tsuJ" tnirp;;;
m! --  lrep/nib/rsu/!#
[download]

I'm a bit surprised darwin doesn't like that. Anyway, here's a modification that doesn't use anything after '/usr/bin/perl' on the same line:

#!/usr/bin/perl  
!m;;;print "Just another Perl hacker"     
;s;
"rekcah lreP rehtona tsuJ" tnirp;;;m!    
lrep/nib/rsu/!#
[download]

An alternative:

#!/usr/bin/perl
print "Just another Perl hacker"
;!q!;
"rekcah lreP rehtona tsuJ" tnirp
lrep/nib/rsu/!#
[download]

#!/usr/bin/perl                         
print "Just another Perl hacker";__END__
__DNE__;"rekcah lreP rehtona tsuJ" tnirp
                         lrep/nib/rsu/!#
[download]

I'm awestuck by the flipped significance of END and DNE
++

#!/usr/bin/perl
BEGIN{close STDERR;print "Just another Perl hacker"}
}"rekcah lreP rehtona tsuJ" tnirp;RREDTS close{NIGEB
lrep/nib/rsu/!#
[download]

You made the same mistake I originally did whilst visually checking my own palindrome: flipping the paired punctuation, that is parenthesis, braces, brackets. See blokhead's initial reply to my OP.

My checker scripts makes it show up a bit better.

jbm@Foucault:~/Code/perl
$ debug=1 ./check_palindrome.pl javafan2.pl 
text = #!/usr/bin/perlBEGIN{closeSTDERR;print"JustanotherPerlhacker"}{
+"rekcahlrePrehtonatsuJ"tnirp;RREDTSclose}NIGEBlrep/nib/rsu/!#
length = 124
middle = 62
half1 = #!/usr/bin/perlBEGIN{closeSTDERR;print"JustanotherPerlhacker"}
half2 = {"rekcahlrePrehtonatsuJ"tnirp;RREDTSclose}NIGEBlrep/nib/rsu/!#
flip  = #!/usr/bin/perlBEGIN}esolcSTDERR;print"JustanotherPerlhacker"{
javafan2.pl: NOT a palindrome.
[download]

Your others check out fine.

jbm@Foucault:~/Code/perl
$ ./check_palindrome.pl javafan*
javafan.pl: Palindome OK.
javafan2.pl: NOT a palindrome.
javafan3.pl: Palindome OK.
javafan4.pl: Palindome OK.
[download]

With all these cool responses, it is clear I needed to write myself a palindrome checker. So here goes.

#!/usr/bin/perl -w

use warnings;
use strict;

my $text;
for my $file (@ARGV) {
  {
    local $/=undef;
    open my $fh, '<', $file or die;
    $text = <$fh>;
    close $fh;
  }
  $text =~ s/\s//g;

  if ($ENV{'debug'}) {
    print "forwards  = $text\n";
    print "backwards = " . reverse($text) . "\n";
  }

  if ($text eq reverse $text) {
    print "$file: Palindome OK.\n";
  }
  else {
    print "$file: NOT a palindrome.\n";
  }
}
exit 0;
[download]

This didn't seem worthy of a separate Cool Uses for Perl posting.

EDIT: Fixed based on JavaFan's comments. I no longer split the text and flip it to compare, and I do a string "is equal" compare instead of re match.

if ($half1 =~ $flip)

Really? It doesn't matter if $flip contain regexp special characters, or if $flip matches $half1 partially?

I'm also wondering why you bother splitting the text into two. Wouldn't something like:

use Test::More;
use autodie;
open my $fh, "<", $file;
undef $/;
$text = <$fh>;
chomp $text;
$text =~ s/\s+//g if $lax_in_whitespace;
ok $text eq reverse $text, "palindrome";
done_testing;
[download]

be enough?

Regarding splitting and flipping it, I guess I was too hung up on the mental steps I was taking to create a palindrome in the first place. I must have coded some analog of what my brain was doing. Twelve hours later, it looks very foolish.

The =~ vs eq bug is just an outright screw up. I have no excuse for that one.