Recursive Regular Expressions

You're replying to a comment by Peteris Krumins.

December 14, 2009, 13:49

Samuel, interesting. I just changed "my $regex" to "$regex" and it works.

$ perl
#!/usr/bin/perl

$str = "0"x50 . "1"x50;
$regex = qr/0(??{$regex})*1/;

if ($str =~ /^$regex$/) {
  print "yes, it matches\n"
}
else {
  print "no, it doesn't match\n"
}

I am not exactly sure why the lexically scoped variable changed whether it matches or not. I am investigating this now.

Update: Can't do that because lexical variables aren't visible during their own initialization! That is, you can't use a lexical in the same statement that declares it. I didn't think about it when I wrote those regexes.

I fixed the article everywhere and it should now be correct. :)

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