Is strict too strict here?

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

Just stumbled across this interesting 'strict' complaint: Let's say I want a module that has a function eval_this() which takes a snippet of code and then eval's it in the main package:

package Foo;
use strict;

sub eval_this {
      my $code = shift;
      $code = "package main; \n$code";
      eval $code;

      die ("Error: $@") if $@;
}

package main;
our $somevar = "somevalue";
Foo::eval_this('print $somevar;');
[download]

Now, as you can see, $somevar has been declared properly as a global in main before the function was called, but yet 'use strict' throws a fatal runtime error:

Variable "$somevar" is not imported at (eval 1) line 2.
Error: Global symbol "$somevar" requires explicit package name at (eval 1) line 2.

Is there a way around this? 'no strict "vars"' would obviously shut strict up, but I would still like strict's variable name checking. Verified with perl-5.10.0.

Comment on Is strict too strict here? Download Code

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Re: Is strict too strict here? by ikegami (Patriarch) on Jul 11, 2008 at 23:52 UTC
`our` is lexically scoped, so it's not in view of the `eval` and thus the code that references `$somevar`. Fix: `Foo::eval_this('our $somevar; print $somevar;');` [download]	[reply] [d/l] [select]
Re^2: Is strict too strict here? by saintmike (Vicar) on Jul 12, 2008 at 00:21 UTC
Fix: Foo::eval_this('our $somevar; print $somevar;'); Yeah, that would work, but that's unfortunately not an option, since I don't know beforehand which variables are used in the eval'd string (well, I guess I could walk main's symbol table and figure out all the declared globals, then add "our $this; our $that" in front of the string, but that's rather ugly. Any other ideas?	[reply]
Re^3: Is strict too strict here? by ikegami (Patriarch) on Jul 12, 2008 at 16:21 UTC
You don't know which variable are used in the evaled string when writing the evaled string? Based on your proposed solution, you'd be happy with "`no strict;`".	[reply] [d/l]
Re: Is strict too strict here? by jettero (Monsignor) on Jul 11, 2008 at 23:45 UTC
No, that's correct. our is a scoped name-space global and your string is evaluated in a different scope. You can either put another our in the eval string or name the package in it (ie, `print $main::somevar`, in which case you don't even need the our). -Paul	[reply] [d/l]
Re: Is strict too strict here? by tilly (Archbishop) on Jul 12, 2008 at 00:22 UTC
Another solution is: `use vars qw($somevar);` [download] In fact I find that preferable to using our, see Why is 'our' good? for why.	[reply] [d/l]
Re: Is strict too strict here? by Joost (Canon) on Jul 12, 2008 at 00:27 UTC
'no strict "vars"' would obviously shut strict up, but I would still like strict's variable name checking. Since strict vars relies on lexical analysis, you have a perverse need to use eval() and you already mentioned that you don't know which variables will be used (how is this in any way realistic again? This seems like a prime example of an XY Problem) you have no choice but to disable strict vars. Luckily you only need it at the eval point: `sub eval_this { my $code = shift; $code = "package main; \n$code"; no strict 'refs'; eval $code; die ("Error: $@") if $@; }` [download] update: you could do: `eval_this('our $var; print $var');` [download] Which doesn't really improve on the situation at all, but would shut up strict. "What should it profit a man, if he should win a flame war, yet lose his cool?"	[reply] [d/l] [select]


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