my $string1 = "abbbbc";

my $found1 = $string1 =~ s/(b*)/^/g;

print "\$string1: $string1, \$found1: $found1"; $found1 is 4

=head

after s///  $string: ^a^^c^
At begin of string
    ...no "b" found |         # satisfies "0 or more 'b's"
         "a" (duh!)  |
     Two "b"(s) found |       # likewise; the first and second 'b's are conflated? 
         and again     |
             "c"        |
     no "b" after "c"    |
=cut