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;
}

[download]

Makeshifts last the longest.

In reply to Re: Finding longest palindrome from a string by Aristotle
in thread Finding longest palindrome from a string by BUU

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