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From Joe Schaefer <>
Subject Re: Getting a / when regex should produce nothing
Date Sun, 25 Apr 2010 12:26:55 GMT
----- Original Message ----

> From: Chris Bennett <>
> To:;
> Sent: Sun, April 25, 2010 8:17:07 AM
> Subject: Re: Getting a / when regex should produce nothing

> Is there a better regex for .?\w?\w?
> I want a . letter letter not . letter 
> or just two letters etc.


> This regex is to prevent read or write access to 
> files up the directory 
> tree or non html files. There is also a username 
> password for any write 
> access.

> undef my $variable is not a common 
> idiom but is seen in Programming Perl 
> and other places. Is there any reason 
> I should use my $variable = undef? 
> More typing. :)

What's wrong with just typing "my $variable;"?

> Why was I getting 
> a / back? Is that an artifact
> from the perl internals?

In your previous code you didn't check that the pattern
had matched before using $1.  In the case when your pattern
doesn't match, $1 remains unchanged from whatever last
set it.  There's probably some code earlier on, or internal
to mod-perl, which does a (successful) pattern match that
sets $1 to "/".

The lesson here should be to always check the return value
of your regexps for success, especially when you've used 
capture variables in your code like $1-$9.


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