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RE: RE: CGI::Carp

by lhoward (Vicar)
on Jul 08, 2000 at 22:48 UTC ( #21662=note: print w/ replies, xml ) Need Help??


in reply to RE: CGI::Carp (use warnings?)
in thread Reviews Quest

My understanding is that as of 5.6 -w on the command line and use warnings in your code are identical. Both "enable many useful warnings". As of 5.6 (maybe earlier, I'm not sure) there is a -W command line option that will "enable all warnings". I do not know if there is a use equivalent to -W.


Comment on RE: RE: CGI::Carp
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RE: RE: RE: CGI::Carp
by SuperCruncher (Pilgrim) on Jul 09, 2000 at 01:31 UTC
    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 blocks etc. Here's an introduction to the new pragma from the What's new in Perl 5.6 page:

    Lexical Warnings

    'Death is not good. I reject death. I will stay away from trucks today.' - lwall

    The way Perl generates warnings has also been completely revised: as a replacement for the -w flag and the $^W special variable, the warnings pragma gives you more flexibility about what warnings you receive and when. In terms of what, you can now specify warnings by category: there are a bunch of standard categories, such as 'syntax', 'io', 'void', and modules will be able to define their own categories. You can also choose to escalate any categories of warning into a fatal error. As for when, the pragma is lexically scoped, so you can switch it on and off as you wish:

    use warnings; $a = @a[1]; # This generates a warning. { no warnings; $a = @a[1]; # This does not. }
    See perllexwarn for how to use this from programs and modules.
RE: RE: RE: CGI::Carp
by SuperCruncher (Pilgrim) on Jul 09, 2000 at 01:15 UTC
    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
    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.

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