sub rosetta_code_new {
    my ( $str ) = @_;
    
    my ( @pal, %seen );
    for my $n ( 0 .. length( $str ) - 1 ) {
        for my $m ( 1 .. length( $str ) - $n ) {
            my $strpal = substr $str, $n, $m;
            push @pal, $strpal
                if $strpal eq reverse $strpal and 
                   not $seen{ $strpal } ++
        }
    }
    
    return @pal
}

##</code><code>##

         Rate rosetta eertree
eertree 1159/s      --    -27%
rosetta 1584/s     37%      --

##</code><code>##

         Rate rosetta eertree
rosetta 387/s      --    -31%
eertree 565/s     46%      --