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Re: [vox-tech] Perl: Regex if then else
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Re: [vox-tech] Perl: Regex if then else

Unfortunately, I don't understand the error, or how to solve it

[jdedev]/home/jstrauss/bin> cat ./tmp
@s = ('initial 256','initial 512','initial 1024','initial 2048');

foreach (@s) {
        s/(?<=initial\s+)(\d+)/$1 == 256 ? "4092" : "1024" /e;
        print "$_\n";

[jdedev]/home/jstrauss/bin> ./tmp
Variable length lookbehind not implemented before HERE mark in regex
m/(?<=initial\s+)(\d+) << HERE / at ./tmp line 14.

----- Original Message -----
From: "Micah Cowan" <micah@cowanbox.com>
To: <vox-tech@franz.mother.com>
Sent: Tuesday, August 14, 2001 12:55 PM
Subject: Re: [vox-tech] Perl: Regex if then else

> On Tue, Aug 14, 2001 at 12:25:48PM -0500, Jay Strauss wrote:
> > Is there any way (in perl) to do a substitution like if you find this,
> > replace it with that, else replace it with something else?
> >
> > For example I have a bunch of lines like:
> >
> > initial 256
> > initial 512
> > initial 1024
> > initial 2048
> >
> > I want to match on /initial\s+\d+/ and replace 256 with 4092 but replace
> > the other numbers with 1024.  I don't know (ahead of time) what the
> > are, I just know I want to replace a specific number with X and the rest
> > with Y.
> You can use s/(?<=initial\s+)(\d+)/ $1 == 256 ? "4092" : "1024" /e;
> The (?<=foo) is a lookbehind assertion, and matches only when the
> pattern is preceded by foo; but isn't itself included in the match
> string.  The 'e' switch allows you to use Perl code to generate the
> substitution.  This is a newer feature, and not available in older
> Perl versions (such as the one I have available at the moment - thus,
> the line above is untested).
> Micah

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