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

This works great perl -e '$x = 8; $xr = "x"; $y = ${ $xr }; print "$y\n";' as expected.

Now, nevermind how silly this seems, I have a good reason which isn't worth explaining... How can I get this to work? 

perl -Mstrict -e 'no strict "refs"; my $x = 8; 
    my $xr = "x"; my $y = ${ $xr }; print "$y\n";'

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(jeffa) Re: scalar ref help?
by jeffa (Bishop) on Dec 16, 2002 at 14:56 UTC
    Use package global variables instead of lexical ones: 
    perl -Mstrict -le 'no strict "refs";use vars qw($x $xr $y);
    $x = 8;$xr = "x"; $y = $$xr; print $y;'

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    Heh heh ... but why?

    jeffa

    L-LL-L--L-LL-L--L-LL-L--
-R--R-RR-R--R-RR-R--R-RR
B--B--B--B--B--B--B--B--
H---H---H---H---H---H---
(the triplet paradiddle with high-hat)
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      perl -Mstrict -le 'no strict "refs";use vars qw($x $xr $y);
    $x = 8;$xr = "x"; $y = $$xr; print $y;'

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      This works because you can only use symbolic references where the variables are visible in the package symbol table; lexical ( i.e. my() ) variables are not (as you can confirm with the Perl debugger).

      Camel 3rd Ed. Ch. 8 refers*

      *Sorry

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Re: scalar ref help?
by Tanalis (Curate) on Dec 16, 2002 at 15:02 UTC
    You can use eval to evaluate a string, not unlike this: 
    use strict;

my $x  = 8;
my $xr = "x";
my $y  = eval "\$$xr";

print $y;

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    You should see that in the code, eval evaluates the string $x and returns the value of the variable, in this case 8.

    Hope that helps ..
    -- Foxcub

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Re: scalar ref help?
by Aristotle (Chancellor) on Dec 16, 2002 at 19:46 UTC

    Just to be sure, I want to advise you to read Dominus' archived newsposts, part one, two and three on Why it's stupid to 'use a variable as a variable name' if you haven't seen any detailed argumentation on the subject yet. There is only very rarely a valid reason to use symbolic references (much less heavy artillery like eval!).

    What you're trying to do can be achieved with a hard reference as well:

    perl -Mstrict -we'my $x = 8; my $xr = \$x; print $$xr, "n";'

    If you already know all this and know that you really need symbolic references, disregard this post (but not without careful reconsideration about whether you really need symrefs :-) ).

    Makeshifts last the longest.

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