Why I can't fetch any special variables ?

PerlOnTheWay has asked for the wisdom of the Perl Monks concerning the following question:

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Re: Why I can't fetch any special variables ? by ikegami (Patriarch) on Sep 15, 2011 at 04:27 UTC
`$<` doesn't get created automatically. Just like with any other variable, you need to use the `G_ADD` flag to create the var if it doesn't exist. The magic will be added automatically when it's created. As for `$^X`, "`^X`" is a convenient way of writing Ctrl-X. Yes, you can use a real Ctrl-X after the `$` in the code, and in fact, that's the real variable name. You'll need to pass `"\cX"` (or whatever the C equivalent is) to `gv_fetchpv`.	[reply] [d/l] [select]
Re^2: Why I can't fetch any special variables ? by PerlOnTheWay (Monk) on Sep 15, 2011 at 04:40 UTC
It works by using `"\030"`	[reply] [d/l]
Re^2: Why I can't fetch any special variables ? by PerlOnTheWay (Monk) on Sep 15, 2011 at 04:56 UTC
Isn't the second parameter of `gv_fetchpv` the default value? How do you specify the `G_ADD` flag?	[reply] [d/l] [select]
Re^3: Why I can't fetch any special variables ? by ikegami (Patriarch) on Sep 15, 2011 at 05:47 UTC
Isn't the second parameter of gv_fetchpv the default value? Say again? What does it mean for a parameter to be a default value? C doesn't have optional parameters, so parameters can't even have default values in C. How do you specify the G_ADD flag? Use it instead of zero for the second argument.	[reply]
Re^2: Why I can't fetch any special variables ? by Anonymous Monk on Sep 15, 2011 at 04:48 UTC
`$<` doesn't get created automatically. Sure it does `perl -le " print defined $<"` As for $^X, "^X" is a convenient way of writing Ctrl-X. Yes, you can use a real Ctrl-X after the $ in the code, and in fact, that's the real variable name. You'll need to pass "\cX"c (or whatever the C equivalent is) to gv_fetchpv. $^X is the actual name of the variable, so no, you don't need to use \cX, you can use $^X, the actual name of the variable	[reply] [d/l] [select]
Re^3: Why I can't fetch any special variables ? by ikegami (Patriarch) on Sep 15, 2011 at 05:41 UTC
Sure it does `perl -le " print defined $<"` No, your use of it created it. Try `perl -E'say for keys %::'` [download] $^X is the actual name of the variable Why are you contradicting two people without proof or argument? `>perl -E"say ${ $::{'^X'} }" >perl -E"say ${ $::{qq{\cX}} }" ...\perl.exe` [download]	[reply] [d/l] [select]
Re^4: Why I can't fetch any special variables ? by Anonymous Monk on Sep 15, 2011 at 06:26 UTC
Re^5: Why I can't fetch any special variables ? by ikegami (Patriarch) on Sep 15, 2011 at 08:00 UTC
Re: Why I can't fetch any special variables ? by ikegami (Patriarch) on Sep 15, 2011 at 06:10 UTC
By the way, `get_sv("<", G_ADD)` is a convenient shortcut (and better documented). Calls `GvSV` for you.	[reply] [d/l] [select]
Re: Why I can't fetch any special variables ? by Anonymous Monk on Sep 15, 2011 at 03:33 UTC
Yes, simply don't PEBKAC-it See How (Not) To Ask A Question	[reply]
Re^2: Why I can't fetch any special variables ? by ikegami (Patriarch) on Sep 15, 2011 at 15:08 UTC
The question is perfectly well phrased. It showed the code he used, the result he expected and the result he got. Runnable demonstrations are always nice, but not necessary.	[reply]