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Postings from August 2009
On Thu, Aug 27, 2009 at 09:33:13AM +0100, Zefram wrote:
> chip@seas.upenn.edu (via RT) wrote:
> >$ perl -p -e 's_/32__;'
>
> The underscore is not perceived as a delimiter there, but as part of
> an identifier. Observe how it was parsed:
>
> $ perl -MO=Deparse -e 's#/32##;'
> s[/32][];
> -e syntax OK
> $ perl -MO=Deparse -e 's_/32__;'
> 's_' / 32;
> -e syntax OK
>
> Other clues are available if you turn on warnings:
>
> $ perl -wce 's_/32__;'
> Misplaced _ in number at -e line 1.
> Misplaced _ in number at -e line 1.
> Useless use of division (/) in void context at -e line 1.
> -e syntax OK
>
> And if the substitution had contained other text then it would have
> blown up earlier:
>
> $ perl -wce 's_\\__;'
> Backslash found where operator expected at -e line 1, near "s_\"
> syntax error at -e line 1, near "s_\"
> -e had compilation errors.
>
> I believe the documentation is at fault. perlop(1) says:
>
> Any non-alphanumeric, non-whitespace delimiter may replace the
> slashes.
>
> Underscore is not alphanumeric or whitespace, but is evidently
> being treated the same way that an alphanumeric character would be.
> The prohibition is really on identifier characters, not alphanumerics.
But even then, the documentation isn't correct. You *can* use word characters
as delimiters:
s _/32__
and
s s/32ss
are fine.
The problem here lies in the tokenization part: the first token of
C<< s_/32__ >> is C<< s_ >>, which isn't the substitution operator.
In fact, this issue isn't any different from saying you cannot use C<< _ >>
as a function argument because you wrote:
C<< func_ >>
which isn't parsed as C<< func (_) >> either.
Abigail
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