Scott E Robinson <[EMAIL PROTECTED]> wrote:
>
> [...] I wonder if there's an easy way to keep the following
> regular expression from matching if the string in the regex
> is null:
>
> $_ = ":B000:L520:M260:M:88:8:M602:";
> $string_to_match="whatever";
> $count = () = /\b($string_to_match)\b/g;
>
> If $string_to_match is null, whatever's in $_ matches it -- and
> for some reason i don't understand it matches twice for every
> colon-delimited piece of $_, though that hardly matters.
Since \b and the empty parens are both zero-width, the expression
will match the beginning and end of each "word".
Put another way, these are all more or less equivalent
/\b/
/\b()\b/
/\b\b\b\b\b\b/
> Is there an easy way to keep the null string from matching
> anything? It would have saved me an evening if I'd known
> about it.
Easier to test $string_to_match before using it in the regex.
if ($string_to_match) {
$count = ...
}
--
Steve
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