A slight modification of my previous entry yields the winning entry (so far). :-)
sub {
my $str = shift;
my $rts = reverse $str;
my $palindrome = '';
my $minlen = 3;
for my $rotate_count ( 0 .. length( $str ) - 1 ) {
my $mask = $str ^ $rts;
# to distinguish adjacent palindromes
substr $mask, $rotate_count, 0, "\1";
while ( $mask =~ /\0{$minlen,}/g ) {
my $offs = $-[0];
--$offs if $offs > $rotate_count; # compensate for mark
+er
$palindrome = substr $str, $offs, $+[0] - $-[0];
$minlen = 1 + length $palindrome;
}
substr $rts, 0, 0, chop $rts;
}
return $palindrome;
}
Makeshifts last the longest.