#!/usr/bin/perl -l

my @L = ( "", qw{ 0 00 11 000 011 110 0000 0011 0110 1001 1100 1111 })
+;

print scalar @L, " with anchors";

for(0..$#L){
   print "$_)'$L[$_]'" if $L[$_] =~ /^(0|1(01*0)*1)*$/;
}

__END__

use YAPE::Regex::Explain;
die YAPE::Regex::Explain->new(qr/(0|1(01*0)*1)*/)->explain;
__DATA__

The regular expression:

(?-imsx:(0|1(01*0)*1)*)

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 (0 or more times
                           (matching the most amount possible)):
----------------------------------------------------------------------
    0                        '0'
----------------------------------------------------------------------
   |                        OR
----------------------------------------------------------------------
    1                        '1'
----------------------------------------------------------------------
    (                        group and capture to \2 (0 or more times
                             (matching the most amount possible)):
----------------------------------------------------------------------
      0                        '0'
----------------------------------------------------------------------
      1*                       '1' (0 or more times (matching the
                               most amount possible))
----------------------------------------------------------------------
      0                        '0'
----------------------------------------------------------------------
    )*                       end of \2 (NOTE: because you're using a
                             quantifier on this capture, only the
                             LAST repetition of the captured pattern
                             will be stored in \2)
----------------------------------------------------------------------
    1                        '1'
----------------------------------------------------------------------
  )*                       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
----------------------------------------------------------------------
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