When in
pause, it means you don't quite understand what the pattern is saying, so it's best to get it explained
#!/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
----------------------------------------------------------------------
As for patterns, well, look at the regex ;D
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** The Third rule of perl club is a statement of fact: pod is sexy.