my $string = "helloworldhellohellohihellohiworld";
my $length = length $string;
my $window = int (($length - 2) / 2);


# use japhy's regex to hoover up all char
# sequences that MIGHT be patterns:

my @pats;
my $regex;
while ($window > 1) {
   $regex = '(?=(' . '.' x $window . '))';
   push @pats, ($string =~ /$regex/g);
   $window --;
}


# now go through @pats to find the duplicates
# and print the final result

@pats = sort @pats;
my %dups;
for (2 .. $#pats) {
    $dups{$pats[$_]} ++ if ($pats[$_] eq $pats[$_ - 1])
}
$dups{$_} ++ for keys %dups;
for (keys %dups) {print $dups{$_},' occurrences of "',$_,'"',"\n"}