Re: [OT] Somehow "reversed" question

On 24 May 2015, Tim Chase <vim@tim.thechases.com> wrote:
> On 2015-05-24 20:26, Meino.Cramer@gmx.de wrote:
> > ...WHOW!.... (an then there was silence)....;)
> >
> > I am completly baffled...that such a simple task in vim "explodes"
> > when one wants to do such a thing with sed. Which is a good
> > argument for vim, indeed!
>
> It's mostly a strong argument for a powerful regular-expression
> engine. Sed's is pretty basic. I was hoping that Perl would make
> it as simple as Vim, but apparently it doesn't support variable-length
> look-behind like Vim:
>
> $ perl -pi -e 's/(?<=^.{20,30})x/y/g'
> Variable length lookbehind not implemented in regex
> m/(?<=^.{20,30})x/ at -e line 1.

However, Perl supports \K, which is essentially the equivalent of
Vim's \zs. It should be enough here.

> so you would have to use
>
> $ perl -pi -e 's/(?<=.{20})(?<!.{30})x/y/g'
>
> which is the generalized case of "there must be at least 20
> characters before the match, but not more than 30 characters
> before the match". It appears to work well for all the odd/degenrate
> edge-cases I listed in my previous email. It's not as elegant as
> the Vim version, but far better than the fragile sed version.
[...]

/lcd

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