delete duplicate in string

#!/usr/bin/env perl
use strict;
use warnings;
use feature q(say);
sub delete_duplicate($);
sub delete_duplicate($) {
  my $s = shift;
  my $len = length $s;
  my $threshold = 5;
  my $t;
  my $found = 0;
  for (my $i = $len / 2; !$found && $threshold <= $i; --$i) {
    for (my $j = 0; $i + $j <= $len; ++$j) {
      $t = substr $s, $j, $i;
      my $c = () = $s =~ /$t/g;
      if ($c > 1) {
        $found = 1;
        last;
      }
    }
  }
  return $s unless $found;
  1 while $s =~ s/(?<=$t)(.*)$t/$1/;
  return $s;
}
say delete_duplicate 'aeaAwww123abcdeあいうえおwww1235www123';
say delete_duplicate 'abcdefabcde';