in reply to Regex quantifiers composed?

I know blakem explained it, but when in doubt,

YAPE::Regex::Explain to the rescue

use YAPE::Regex::Explain;
my $regex = '/^([0-9]+)\.([0-9]+)\s+date\s+(\d\d(\d\d)?(\.\d\d){5}?);$
+/o';
#print YAPE::Regex::Explain->new($regex)->explain;
$regex = '(\.\d\d){5}?;';
print '#' x 60,"\n";
print YAPE::Regex::Explain->new($regex)->explain;
print '#' x 60,"\n";
print YAPE::Regex::Explain->new(qr/a{1,5}/)->explain;
print '#' x 60,"\n";
print YAPE::Regex::Explain->new(qr/a{1,5}?/)->explain;
__END__

[download]
############################################################
The regular expression:

(?-imsx:(\.\d\d){5}?;)

matches as follows:

NODE                     EXPLANATION
----------------------------------------------------------------------
(?-imsx:                 group, but do not capture (case-sensitive)
                         (with ^ and $ matching normally) (with . not
                         matching \n) (matching whitespace and #
                         normally):
----------------------------------------------------------------------
  (                        group and capture to \1 (5 times):
----------------------------------------------------------------------
    \.                       '.'
----------------------------------------------------------------------
    \d                       digits (0-9)
----------------------------------------------------------------------
    \d                       digits (0-9)
----------------------------------------------------------------------
  ){5}?                    end of \1 (NOTE: because you're using a
                           quantifier on this capture, only the LAST
                           repetition of the captured pattern will be
                           stored in \1)
----------------------------------------------------------------------
  ;                        ';'
----------------------------------------------------------------------
)                        end of grouping
----------------------------------------------------------------------
############################################################
The regular expression:

(?-imsx:a{1,5})

matches as follows:

NODE                     EXPLANATION
----------------------------------------------------------------------
(?-imsx:                 group, but do not capture (case-sensitive)
                         (with ^ and $ matching normally) (with . not
                         matching \n) (matching whitespace and #
                         normally):
----------------------------------------------------------------------
  a{1,5}                   'a' (between 1 and 5 times (matching the
                           most amount possible))
----------------------------------------------------------------------
)                        end of grouping
----------------------------------------------------------------------
############################################################
The regular expression:

(?-imsx:a{1,5}?)

matches as follows:

NODE                     EXPLANATION
----------------------------------------------------------------------
(?-imsx:                 group, but do not capture (case-sensitive)
                         (with ^ and $ matching normally) (with . not
                         matching \n) (matching whitespace and #
                         normally):
----------------------------------------------------------------------
  a{1,5}?                  'a' (between 1 and 5 times (matching the
                           least amount possible))
----------------------------------------------------------------------
)                        end of grouping
----------------------------------------------------------------------

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