Lookbehinds not recognized?

reptile has asked for the wisdom of the Perl Monks concerning the following question:

This is strange and I can't figure out why it would be doing this. I have perl 5.00405 which I know includes lookbehind assertions, but nonetheless, gives me this error:

if ( /(?<!foo)bar/ )
Sequence (?<...) not recognized at - line 1.
[download]

Does anyone have a clue why this would happen? I'm using the same example given on the perlre manpage from the 5.00401 docs and it doesn't work.

Comment on Lookbehinds not recognized? Download Code

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Re: Lookbehinds not recognized? by chromatic (Archbishop) on May 14, 2000 at 04:13 UTC
After checking perldelta for 5.005_3 and Elements of Programming with Perl, I have to conclude that lookbehind assertions were introduced in 5.005. Lookaheads were around before that, though. As to why perlre for 5.004 shows that -- your guess is as good as mine.	[reply]
RE: Re: Lookbehinds not recognized? by reptile (Monk) on May 14, 2000 at 04:56 UTC
I guess you're right. 5.005 works, I just installed it. I have no idea why the 5.004 docs say it was in there. Looks like I'm spending the rest of the night reinstalling modules. Thanks.	[reply]
RE: Re: Lookbehinds not recognized? by mdillon (Priest) on May 14, 2000 at 04:21 UTC
it seems to have been added in 5.004_50, which i think is a prerelease of the 5.005 series. here's the relevant message from perl5-porters. see item (k).	[reply]
Re: Lookbehinds not recognized? by httptech (Chaplain) on May 14, 2000 at 06:47 UTC
I had a similar question a few days ago, and mdillon gave me some examples But you will need to upgrade Perl as he stated above.	[reply]
RE: Lookbehinds not recognized? by undefined (Novice) on May 15, 2000 at 03:41 UTC
Hello! Are you using perldoc on your system or the Perl Monks web version? I think (look at Perl Monks perldelta page) the web version you reference is really 5.005 rather than 5.004 which may be your problem. I tried it out on 5.005_03 and it works as it should. I dont have an older version so I can't say for sure... Good Luck with it!! Check out Knexa.com KNowledge EXchange Auction (Preview Release)	[reply]