#  https://theweeklychallenge.org/blog/perl-weekly-challenge-340/
use v5.12;
use warnings;

for ('abbaca','azxxzy','aaaaaaaa','aabccba','abcddcba') {
  my $str = $_;
  say "*** Input: $str";
  while ($str =~ s/(\w)\1+//g) {
    say "Remove '$&' => '$str'"
  } ;
  say "Output: '$str'\n\n";
}