in reply to How to think.
You might design the industry-strength application?
Actually you need modularity and scalability then.
The application should remain maintanable and flexible.
You do need design patterns!
But be aware that Perl design patterns are quite idiomatic:)
They differ from C++ design patterns.
So use the perlish patterns and build the application.
The key word is 'to build' the application instead of to 'to code'.
There is an entry point:
http://www.slowass.net/wiki2/assemble.cgi?PerlDesignPatterns
The good idea is to avoid them all at once.
Different layers require different set of patterns.
And different application scale also want various approaches.
Thats it.
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Seekers of Perl Wisdom