Results for string:

"aabcdabcabcecdecd "

          Rate  blazar  kramba ikegami   lodin     oha
blazar   464/s      --    -77%    -89%    -90%    -90%
kramba  2062/s    344%      --    -52%    -54%    -58%
ikegami 4255/s    817%    106%      --     -4%    -13%
lodin   4444/s    858%    116%      4%      --     -9%
oha     4878/s    951%    137%     15%     10%      --

Results for string:

"aabcdabcabcecdecd aabcdabcabcecdecd "

          Rate  blazar     oha  kramba ikegami   lodin
blazar  92.4/s      --    -85%    -86%    -86%    -87%
oha      610/s    560%      --     -7%     -9%    -14%
kramba   658/s    612%      8%      --     -1%     -7%
ikegami  667/s    621%      9%      1%      --     -6%
lodin    709/s    667%     16%      8%      6%      --

Results for string:

"aabcdabcabcecdecd aabcdabcabcecdecd aabcdabcabcecdecd aabcdabcabcecdecd "

          Rate  blazar   lodin ikegami     oha  kramba
blazar  21.4/s      --    -85%    -86%    -86%    -90%
lodin    144/s    574%      --     -3%     -5%    -35%
ikegami  148/s    594%      3%      --     -2%    -33%
oha      151/s    607%      5%      2%      --    -31%
kramba   220/s    930%     53%     48%     46%      --


##</code><code>##

#!/usr/bin/perl
use strict;
use warnings;
use Data::Dumper;
use constant MIN_LENGTH => 2;
use constant MIN_REPEATS => 2;
use Benchmark qw/:all :hireswallclock/;

my $str='aabcdabcabcecdecd';

sub blazar {
    local $_=shift;
    my $l=length;
    my %count;

    for my $off (0..$l-1) {
        for my $len (MIN_LENGTH .. $l-$off) {
            my $s = substr $_, $off, $len;
            $count{ $s } ||= ()= /$s/g;
        }
        $count{$_} < MIN_REPEATS and
          delete $count{$_} for keys %count;
    }
    \%count;
}

sub oha {
    my $s=shift;
    my %saw;

    while($s =~ /(..+)(?=.*?\1)/g) {
        for my $x (0..length $1) {
            @saw{ map {substr $1, $x, $_} $x+2..length $1 } = ();
        }
    }
    $saw{$_} =()= $s =~ /\Q$_/g for keys %saw;
    \%saw;
}

sub ikegami {
    my $str = shift;

    local our %counts;
    $str =~ /
      (.{2,})   # or (.+)
      (?(?{ !$counts{$1} })(?=.*\1))
      (?{ ++$counts{$1} })
      (?!)
      /x;
    \%counts;
}

sub lodin {
    my $str = shift;

    local our %count;
    $str =~ /
      (.{2,})
      (?(?{ $count{$1} })
          (?!)
      )
      .*
      \1
      (?{ ($count{$1} ||= 1)++ })
      (?!)
      /x;
    \%count;
}


{
    my %count;

    sub kramba {
        my( $string) = @_;
        my $length = length( $string );

        if ($length < MIN_LENGTH) {
            for (keys %count) {
                delete $count{$_}
                    if $count{$_} < MIN_REPEATS;
            }
            return \%count;
        }

        for my $l (MIN_LENGTH..$length) {
            my $s = substr( $string, 0, $l );
            $count{ $s } += 1;
        }

        kramba( substr( $string, 1 ) );
    };
}

for my $multiplier (1, 2, 4) {
   my $work_str = "$str " x $multiplier;

print "Results for string:\n\n\"$work_str\"\n\n";
    cmpthese 2000/$multiplier => {
        blazar  => sub { blazar $work_str },
        oha     => sub { oha $work_str },
        kramba  => sub { kramba $work_str },
        ikegami => sub { ikegami $work_str },
        lodin   => sub { lodin $work_str },
    }
}