Warnings using -w

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

Hi Monks!

This test script is to ask what would be an alternative and why I get this warning message:
Use of uninitialized value $_[0] in string eq at /usr/local/share/perl5/CGI.pm line 2209. if I use "-w".
If I remove the "-w" and use instead "use warnings" I don't get the warning, is it because of CGI.pm been deprecated?
The version of Perl I have is v5.10.1
Any suggestions?

#!/usr/bin/perl -w

use strict;

use CGI qw(:standard);
use CGI::Carp qw( fatalsToBrowser set_message );

my $q = new CGI;

print $q->header();

my $msg   = escapeHTML( scalar $q->param( 'msg' )) || 'No Msg';
my $error = escapeHTML( scalar $q->param( 'error' )) || ' No error';

my $error_msg = ($msg) ? $msg : ($error) ? $error : '';

print "<br><br>Msgs: $error_msg <br><br>";

exit;
[download]

Thanks for looking!

Comment on Warnings using -w Select or Download Code

Replies are listed 'Best First'.
Re: Warnings using -w by Anonymous Monk on Jun 26, 2017 at 14:14 UTC
It's because the effect of -w is global and "use warnings" is only for the lexical scope. That's why "use warnings" is recommend nowadays.	[reply]
Re: Warnings using -w by ikegami (Patriarch) on Jun 26, 2017 at 20:11 UTC
`-w` activates warnings globally, which causes `escapeHTML` to warn when you pass `undef` to it. Fixed: `my $msg_html = escapeHTML( $q->param( 'msg' ) // 'No msg' ); my $error_html = escapeHTML( $q->param( 'error' ) // 'No error' );` [download]	[reply] [d/l] [select]
Re: Warnings using -w by Discipulus (Canon) on Jun 26, 2017 at 14:15 UTC
Hello, just some hint.. I suppose it is not because the module is deprecated: this is just an advice with no consequences. The fact you observe can be related to the server which serve the script; I dont know how the shebang is taken in consideration while the script is run into a web server: some of them, for sure, ignore it completely. The error is anyway strange.. Which webserver are you using to serve the program? is something in the middle (like mod_perl)? More info you pass more easy you'll get the anser you need. L* There are no rules, there are no thumbs.. Reinvent the wheel, then learn The Wheel; may be one day you reinvent one of THE WHEELS.	[reply] [d/l]
Re^2: Warnings using -w by Anonymous Monk on Jun 26, 2017 at 14:35 UTC
Nothing in the middle, using Apache Server.	[reply]