#!/usr/bin/perl

use strict;
use warnings;
use Data::Dumper;
use constant MIN => 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 .. $l-$off) {
            my $s=substr $_, $off, $len;
            $count{ $s } ||= ()= /$s/g;
        }
        $count{$_} == 1 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;
}

{
    my %count;
    sub count1 {
        my( $string) = @_;
        my $length = length( $string );
        
        if ($length < MIN) {
            $count{$_} == 1 and delete $count{$_} for keys %count;
            return \%count;
        }
        
        for my $l (MIN..$length) {
            my $s = substr( $string, 0, $l );
            $count{ $s } += 1;
        }
        count1( substr( $string, 1 ) );
    }

    sub kramba {
        count1 shift;
        for (keys %count) {
            delete $count{$_} unless
              $count{$_} >= 2 and length($_) >= MIN;
        }
        \%count;
    }
}

sub ikegami {
    my $str = shift;

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

cmpthese 10_000 => {
    blazar  => sub { blazar $str },
    oha     => sub { oha $str },
    kramba  => sub { kramba $str },
    ikegami => sub { ikegami $str },
};
    
__END__
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sub lodin {
    my $str = shift;

    local our %count;
    $str =~ /
      (.{2,})
      (?(?{ $count{$1} })
          (?!)
      )
      .*
      \1
      (?{ ($count{$1} ||= 1)++ })
      (?!)
      /x;
    \%count;
}
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sub kramba {
    my %count;
    my $count;
    $count = sub {
        my( $string) = @_;
        my $length = length( $string );
        
        if ($length < MIN) {
            $count{$_} == 1 and delete $count{$_} for keys %count;
            return \%count;
        }
        
        for my $l (MIN..$length) {
            my $s = substr( $string, 0, $l );
            $count{ $s } += 1;
        }
        $count->( substr( $string, 1 ) );
    };
    $count->(shift);
    for (keys %count) {
        delete $count{$_} unless
          $count{$_} >= 2 and length($_) >= MIN;
    }
    \%count;
}
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