-w turns warnings on for the entire program, while use warnings; only turns on warnings for the current /scope|module|file/.

Update:Meh, late on the post.  First post describes it better (if better is defined as using Perl compliant language :) ).

In reply to Re: Difference between 'use warnings' and '-w' switch by northwind
in thread Difference between 'use warnings' and '-w' switch by muntfish

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