D'oh, the proper post is 'below' this one, sorry

As far as I know, the use warnings pragma was introduced as:

- it is easier for people who are on non 'shebang supporting' systems to use.
- it can be disabled for certain sections of code, e.g.

use strict;
use warnings; 

print $foo;   # Warning here, undefined value

no warnings; 
print $foo;   # No warning now 

use warnings; 
print $foo;  # Warning again
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On systems that don't support the UNIX shebang, it is a pain having to manually type in

perl -w foo.pl

every time you want warnings. If you can just use the pragma, it is easier.