Re^5: Regex conditional match if previous match in same expression is true?

Rhandom provided a better solution. Here's a simplification of it:

/
   (?: ({) | (?<!{) )
   hello
   (?(1) } | (?!}) )
/x
[download]

It doesn't "use Perl", but I suspect it won't solve your compatibility problems like you think it will. Are you sure that engine supports conditionals ((?(...)...|...))?

I've never read "Mastering Regular Expressions".

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Re^6: Regex conditional match if previous match in same expression is true? by radiantmatrix (Parson) on Apr 23, 2007 at 14:25 UTC
Yes, the Jakarta-ORO provides a `Perl5Matcher` class (and relatives) that supports all of the Perl-5 regex engine, with the (fairly obvious) exception of being able to execute Perl inside a regex. It's been a lifesaver on one of my current projects, where I have to use Java (plugins for a J2EE app, plus boss requirement) to do tasks particularly suited to regexen. I'm thankful to the Jakarta folks for making it so that I don't have to learn Yet Another Regex Syntax. ;-) <–radiant.matrix–> Ramblings and references The Code that can be seen is not the true Code I haven't found a problem yet that can't be solved by a well-placed trebuchet	[reply] [d/l]

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Re^6: Regex conditional match if previous match in same expression is true?
by radiantmatrix (Parson) on Apr 23, 2007 at 14:25 UTC

Yes, the Jakarta-ORO provides a Perl5Matcher class (and relatives) that supports all of the Perl-5 regex engine, with the (fairly obvious) exception of being able to execute Perl inside a regex.

It's been a lifesaver on one of my current projects, where I have to use Java (plugins for a J2EE app, plus boss requirement) to do tasks particularly suited to regexen. I'm thankful to the Jakarta folks for making it so that I don't have to learn Yet Another Regex Syntax. ;-)

<–radiant.matrix–>
Ramblings and references
The Code that can be seen is not the true Code
I haven't found a problem yet that can't be solved by a well-placed trebuchet

[reply]
[d/l]