Good morning,

I was trying to find out how Exporter manages to prevent the calling module from "strict vars" errors, so that the calling module may use the imported variables without declaring them.

So I wrote a file called "imp.pl":

package imp;
*main::foo = \42;

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Then I tried 

perl -le 'BEGIN { require "imp.pl"}; use strict; print $foo'

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and it printed 42. Now that's cool: I may use $foo without declaring it, merely because it exists in my namespace.

However, removing the first line "package imp;" from imp.pl, I get those errors:

perl -le 'BEGIN { require "imp.pl"}; use strict; print $foo'
Variable "$foo" is not imported at -e line 1.
Global symbol "$foo" requires explicit package name at -e line 1.
Execution of -e aborted due to compilation errors.

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So, the exporting doesn't work within the "main" package, which appears very strange to me. Even more curious, perl does seem to recognize that I tried to import the variable, because it prints "...is not imported...". This warning isn't printed for other variables:

perl -le 'BEGIN { require "imp.pl"}; use strict; print $bar'
Global symbol "$bar" requires explicit package name at -e line 1.
Execution of -e aborted due to compilation errors.

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Extract from perldiag:

Variable "%s" is not imported%s
(F) While "use strict" in effect, you referred to a global variable that you apparently thought was imported from another module, because something else of the same name (usually a subroutine) is exported by that module. It usually means you put the wrong funny character on the front of your variable.

Obviously, I did not put the wrong funny character.

Could anyone please shed light into this darkness of perl's? Thank you very much.

Update: Using perl -MO=Deparse on imp.pl, I see that *main::foo is optimized to *foo. However, without a package line, this shouldn't make any difference.

In reply to How to trick strict like Exporter does by betterworld

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