If ModA uses ModB and ModB uses ModA, you'll have problems exporting symbols. The best way I've found is to do: 
# ModA.pm

use strict;
use warnings;

package ModA;

BEGIN {
   our @ISA = qw( Exporter );
   our @EXPORT_OK = qw( ... );
   require Exporter;
}

use This;
use ModB;
use That;

...

1;

[download]
# ModB.pm

use strict;
use warnings;

package ModB;

BEGIN {
   our @ISA = qw( Exporter );
   our @EXPORT_OK = qw( ... );
   require Exporter;
}

use This;
use ModA;
use That;

...

1;

[download]

Otherwise, things usually work out fine.

In reply to Re: Understanding order of module compilation and execution by ikegami
in thread Understanding order of module compilation and execution by Anonymous Monk

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