Difference between warnings pragma or enabling warnings using -w switch?

gube has asked for the wisdom of the Perl Monks concerning the following question:

Replies are listed 'Best First'.
Re: Difference between warnings pragma or enabling warnings using -w switch? by rupesh (Hermit) on Aug 30, 2005 at 05:16 UTC
gube, The -T command line switch turns on taint checking, something that's useful for CGIs when you want to make sure there's no user input that can possibly flow through to the operating system for security reasons. Typically you want to enable taint-checking as early in the command line options as possible. -w enables warnings globally for the perl interpreter. It can be used for code that needs to maintain compatability with 5.005 and older perls, but for newer code, use warnings is better, because it will not enable warnings in parts of the program that are not designed to be run with them enabled. The -w has a global effect on your entire program. The warnings pragma was introduced in Perl 5.6 and allows for scoped sections of warning-enabled code, with the ability to turn on and off specific classes of warning messages. On more information on use warnings, you can visit this node --> here. Cheers, Rupesh.	[reply]
Re: Difference between warnings pragma or enabling warnings using -w switch? by tlm (Prior) on Aug 30, 2005 at 10:24 UTC
See the thread #!/usr/bin/perl -w and use warnings;. the lowliest monk	[reply]
Re: Difference between warnings pragma or enabling warnings using -w switch? by pg (Canon) on Aug 30, 2005 at 05:31 UTC
Create two pieces of code, test1.pl and blah.pm: `use warnings; use blah; sprintf("%d\n", 1); #this is always warned, as it is in a scope with " +use warnings" declared` [download] And here is blah.pm: `package blah; sprintf("%d\n;", 1); 1;` [download] Run perl test1.pl, you get: `Useless use of a constant in void context at test1.pl line 5.` [download] With perl -w test1.pl, you get: `Useless use of a constant in void context at blah.pm line 3. Useless use of a constant in void context at test1.pl line 5.` [download]	[reply] [d/l] [select]
Re^2: Difference between warnings pragma or enabling warnings using -w switch? by Taulmarill (Deacon) on Aug 30, 2005 at 08:46 UTC
i'd like to add, that you could say `no warnings;` in blah.pm, which would turn off the warnings for the enclosing block.	[reply]
A reply falls below the community's threshold of quality. You may see it by logging in.