++ on the Best Practices suggestion.

I think this situation is a good candidate for using exported symbols. Have package moduleA export $readMode, etc. which other modules can import. The implementation would go something like: 

package moduleA;

@ISA = qw(Exporter);
@EXPORT_OK = qw($readMode $writeMode $appendMode openFile);
$readMode = '';
$writeMode = '>';
...
1;

[download]
Then other modules can selectively import them into their own namespace via: 
use moduleA qw($appendMode openFile);
...
# calls moduleA::openFile() with parameter $moduleA::appendMode:
openFile(..., $appendMode); # note: no namespace qualifier needed

[download]

In reply to Re: Using Global Variables in Perl by pc88mxer
in thread Using Global Variables in Perl by gzayzay

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