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use strict;
use warnings;
...
$str = q{aabbbbcddddddee};
$str =~ s/((.)\2{2})\2+/$1/g;
print qq{Corrected regex\n  $str\n};

Starting string
  aabbbbcddddddee
...
  aabbbbcddddddee
Corrected regex
  aabbbcdddee