I *think* I know why this is going on, but I would like someone smarter than me to explain it. I have spent some time reading documentation and did not find anything that explained this exact scenario.

Consider... Executing this code: 
# Main script
require 'TEST2.pm';
require 'TEST.pm';

test_sub();

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produces the error "Undefined subroutine &main::test_sub called..."

The subroutine test_sub lives in the TEST package within TEST.pm, and is exported: 
# TEST.pm

*test_sub = *TEST::test_sub;

package TEST;

sub test_sub {
  print "Hello, world!\n";
}

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and the contents of TEST2.pm: 
# TEST2.pm
package TEST2;

require 'TEST.pm';

return 1;

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So the main script requires TEST2.pm, which requires TEST.pm from within the TEST2 package. Then the main script requires TEST.pm, which is responsible for exporting the test_sub() subroutine. But it does not work. If I reverse the two require's in the main script, the call to test_sub() will work, but calling it from TEST2 will not work. I am under the impression that the first time require is called for TEST.pm (from the TEST2 package in TEST2.pm), test_sub() is exported to TEST2. When the main script then attempts to require TEST.pm, it is skipped because it has already been require'd. This means the main script cannot find test_sub() (unless the call to it is fully-qualified.) Is this the right reason for this behavior, or is something else going on? And is there any way to get the test_sub() subroutine to be recognizable from both the main script and the TEST2 package, without using a fully-qualified call?

In reply to Requiring libraries that export subroutines, and are required by other libraries... Exported subs cannot be found? by RP31

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