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Re: Common Regex Gotchas

by rovf (Priest)
on Jul 07, 2008 at 08:59 UTC ( #695930=note: print w/replies, xml ) Need Help??


in reply to Common Regex Gotchas

Maybe it's worth to include the following, which has bitten me once too: One common use is to get regexp from an external source - for instance, your commandline - into your program, so you end up having somewhere something like:

if($line =~ /$pattern/) { ... }
The trap here is when $pattern happens to be the null string, yielding the Regexp //. This special regexp, unless it is used as argument to the split function, means: "Match again the most recently encountered regexps", which can lead to pretty bizarre program behaviour.

-- 
Ronald Fischer <ynnor@mm.st>

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[Corion]: Oh yay. I wonder why a very simple change in a program doesn't elicit a diff, and now I see that my diff program seems to have a bug ;)
[1nickt]: marto thanks for asking, so far so good. A pretty modern stack and decent procedures, although rather too much home-built stuff (e.g. a logging role that should tries to duplicate Log::Any).
[Corion]: No. It's just that I'm comparing the same output file twice, instead of comparing the output files of the two runs %-)
[Corion]: Lo and behold, running a program with the correct input files yields the correct (and expected) output. Yay me.
[1nickt]: Got a MacBook and am expected to develop directly on it, ironic given the recent thread about that.
[marto]: Corion, some not too serious issues with the kids, hopefully, other than that just dealing with commuting by car again in the winter, not much fun so far, and there's no real 'bad' weather yet :)
[marto]: 1nickt, glad to hear it, I'm sure you'll bring improvements to their stack in due course ;)
[1nickt]: Just trying to adjust to a new culture. Better doc than I am used to , but quite a bit more Agiley meta-bullshit; at least half a dozen meetings a week, strict "sprint" schedule etc. I'll adjust. And I hope to just switch off after the "scrum" each day at
[1nickt]: ... the end of the afternoon. marto How are you, snowed in? Mum and Dad expecting snow today in Surrey. (Have 5" on the ground here in NJ. And my son's high school in SOCal closed until after Xmas due to fires.)
[Corion]: 1nickt: In a sense the meta-bullshit might even be beneficial to you as you get to hear the cow-orkers talk (or not talk) about the issues you perceive. I think Agile is mostly about the meta ;)

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