[Israel.pm] Selective warnings use

[Madani, Srikanth, VF-DE]

Mikhael Goikhman wrote:
 
>Direct use of $] is possible, of course. This condition is portable:
> if $] < 5.006;

True, thanks.

>So, the following line should do what you wanted:
> eval "use warnings;" if $] >= 5.006;

I can't seem to get this to work. Can you please explain the behaviour
below:

DevSet> cat war4.pl
#!/usr/local/bin/perl
use strict;
eval "use warnings;" if $] >= 5.006;
print "\nThe value of warnings is $^W\n";
$a =+ 2;
DevSet>
DevSet>
DevSet> ./war4.pl

The value of warnings is 0
DevSet>


The reversed operator causes no concern here. Whereas, if I use the
"warnings" pragma directly (as opposed to eval'ing it):


DevSet> cat war41.pl
#!/usr/local/bin/perl
use strict;
use warnings;
print "\nThe value of warnings is $^W\n";
$a =+ 2;
DevSet>
DevSet>
DevSet> ./war41.pl
Reversed += operator at ./war41.pl line 5.
Name "main::a" used only once: possible typo at ./war41.pl line 5.

The value of warnings is 0
DevSet>


Both these snippets were run on version 5.008001 (Perl v5.8).



>Similarly, $^W = 0; may be used for "no warnings;". But this is not the
>official way, working with this variable directly is not very portable.

That's what I found too. A 'use diagnostics' pragma affects the value of
this variable, globally.
Anyway, this whole thread is basically about style and portability. :-)



Thanks,
Srikanth Madani