Re^2: RegEx - match !foo followed by foo

Thanks Corion, but I don't think either merlyn's or your solution works... also I made one mistake in my examples:

foobar:helloworldgonk shouldn't match, because neither gonk nor @ can be found after no more than 5 preceding characters

Merlyn's solution fails (afaik) because it doesn't require the non-gonk to be followed by gonk (or @).

Your solution fails (afaik) because foobar:gonkgonk would return 'foobar:gonk' (and should return nothing).

To put it another way, if 'gonk' was a single character (say 'Ł'), then I would do:

/foobar:[^Ł@]{1,5}[Ł@]/
[download]

Hope that makes it clearer

Tom Melly, tom@tomandlu.co.uk

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Re^3: RegEx - match !foo followed by foo by Corion (Patriarch) on Mar 16, 2006 at 13:36 UTC
There are the edge cases of `foobar:gonkogonk` and `foobar:ogonkgonk`, which I've added to my below test cases. You need to decide if `gonkogonk` and `ogonkgonk` should be rejected or accepted. My solution rejects the first but accepts the second case. `use strict; use Test::More tests => 6; sub ungonk { local $_ = $_[0]; if (/^(foobar:(?!gonk).{1,5})gonk$/) { return $1 } else { return undef }; }; is ungonk('foobar:hellogonk'), 'foobar:hello'; is ungonk('foobar:gonk'), undef; is ungonk('foobar:higonk'), 'foobar:hi'; is ungonk('foobar:helloworldgonk'), undef; is ungonk('foobar:gonkgonk'), undef; is ungonk('foobar:gonkogonk'), undef; is ungonk('foobar:ogonkgonk'), 'ogonk';` [download] Update: After reading your specification again, you don't want `gonk` to be found within the first five characters, but it must appear at the end. I think the below program does that, and rejects `:ogonkgonk` and `:gonkogonk`. `use strict; use Test::More tests => 7; sub ungonk { local $_ = $_[0]; if (/^(foobar:(?:(?!gonk).){1,5})gonk$/) { return $1 } else { return undef }; }; is ungonk('foobar:hellogonk'), 'foobar:hello'; is ungonk('foobar:gonk'), undef; is ungonk('foobar:higonk'), 'foobar:hi'; is ungonk('foobar:helloworldgonk'), undef; is ungonk('foobar:gonkgonk'), undef; is ungonk('foobar:gonkogonk'), undef; is ungonk('foobar:ogonkgonk'), undef;` [download]	[reply] [d/l] [select]
Re^4: RegEx - match !foo followed by foo by Melly (Chaplain) on Mar 16, 2006 at 13:45 UTC
Hmm, almost - and may be enough for me to work it out <thinks>...</thinks> Nope, still stuck foobar:ogonkgonk should return foobar:o Tom Melly, tom@tomandlu.co.uk	[reply]
Re^5: RegEx - match !foo followed by foo by Corion (Patriarch) on Mar 16, 2006 at 13:49 UTC
The following passes the modified test suite. `use strict; use Test::More tests => 7; sub ungonk { local $_ = $_[0]; if (/^(foobar:(?:(?!gonk).){1,5})gonk/) { return $1 } else { return undef }; }; is ungonk('foobar:hellogonk'), 'foobar:hello'; is ungonk('foobar:gonk'), undef; is ungonk('foobar:higonk'), 'foobar:hi'; is ungonk('foobar:helloworldgonk'), undef; is ungonk('foobar:gonkgonk'), undef; is ungonk('foobar:gonkogonk'), undef; is ungonk('foobar:ogonkgonk'), 'foobar:o';` [download]	[reply] [d/l]
Re^6: RegEx - match !foo followed by foo by Melly (Chaplain) on Mar 16, 2006 at 13:57 UTC