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Re: [perl #21053] Lexical scoping bug concerning eval

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Dave Mitchell
February 17, 2003 05:44
Re: [perl #21053] Lexical scoping bug concerning eval
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On Sat, Feb 15, 2003 at 03:13:43AM -0000, (via RT) wrote:
> Hi, I am reporting a lexical scoping bug of a nasty nature.
> I am running Perl v5.6.1 on a redhat 7.3 i386-Linux platform.
> Synopsis:
> Given a variable in package B, used from package A, package A can't access it
> in via an eval statement.
> Example:
> Here is the short and sweet (or not so sweet)! version:
> #!/usr/bin/perl
> package B;
> my $answer = 42;
> 1;
> package A;
> sub fn{
> 	print "answer=" . eval ('$B::answer') . "\n";
> 	print "answer=" . eval ('package B; $answer') . "\n";
>  }
> 1;
> package main;
> A::fn();
> 1;
> __FILE__ENDS__
> this prints:
> answer=
> answer=42

Thanks for the report; however, this is not a bug, as you have confused
lexical variables with package (global) variables.

lexical variables are declared with 'my', and are valid only for the
current lexical scope, ie until the next block end, sub end or file end,
whichever comes first - and they are not visible from other files.
They do not live in any package.

Global variables are accessible from all files and all parts of a program;
and are normally specified as package_name::variable_name; however, as
a convenience, you can drop the package_name:: prefix is that happens to
be the current package.

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