sub findCycle searches a string to determine if it is comprised of a pattern repeated two or more times and returns the pattern length and the pattern.

If there is not a repeating pattern, the length of the string and the entire string are returned.

use strict;
use warnings;

while (<DATA>)
  {
  chomp;
  my ($pattern, $cycleLen) = findCycle ($_);
  print "$_ -> $pattern ($cycleLen)\n";
  }


sub findCycle
{
my $str = shift;
my $copy = $str;
my $cycleLen = 0;
my $strLen = length ($copy);

for (0..($strLen - 1))
  {
  $copy .= substr $copy, 0, 1, '';
  $cycleLen = $_ + 1;
  ($str ^ $copy) =~ /^\0*/;
  return wantarray  ? ($cycleLen, substr $str, 0, $cycleLen)
                    : $cycleLen if $+[0] == $strLen;
  }

return wantarray ? ($strLen, $str) : $strLen;
}
__DATA__
TTTTT
ATATAT
ATTATTATT
123412341234
123456

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In reply to Find repeated patterns in strings by GrandFather

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