DB<134> p $in
ZBBBCZZ
  DB<135> x split /(?<=(.))(?!\1)/, $in
0  'Z'
1  'Z'
2  'BBB'
3  'B'
4  'C'
5  'C'
6  'ZZ'
7  'Z'

##</code><code>##

  DB<137> use List::Util qw/pairkeys pairvalues/

  DB<138> x pairkeys  split /(?<=(.))(?!\1)/, $in
0  'Z'
1  'BBB'
2  'C'
3  'ZZ'
  DB<139> x pairvalues  split /(?<=(.))(?!\1)/, $in
0  'Z'
1  'B'
2  'C'
3  'Z'
  DB<140>

##</code><code>##

  DB<8> use List::Util qw/pairkeys/

  DB<9> $_='ZBBBCZZ'

  DB<10> x pairkeys /((.)\2*)/g
0  'Z'
1  'BBB'
2  'C'
3  'ZZ'
  DB<11>