(...)?, (...)*, etc don't really make any sense.
((?:...)?), ((?:...)*), etc would properly capture.

Did you mean (b*?)?

if ("abbbbbc" =~ /(b*?)(b*?)c/) {
   print("\$1 eq '$1'\n");   # $1 eq ''
   print("\$2 eq '$2'\n");   # $2 eq 'bbbbb'
} else {
   print("No match\n");
}
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I'd file this under GIGO, but Perl has been changed to return a more sensible result in newer versions.