How exactly does no work?

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

use strict;                                                           
+          
use warnings;

sub c {
    no warnings;
    print $d; 
}
sub a{
    no warnings;
    print $b; 
    c;  
}
a();

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Replies are listed 'Best First'.
Re: How exactly does no work? by moritz (Cardinal) on Feb 16, 2012 at 11:24 UTC
Warnings are not errors, and errors are not warnings. The fatal error comes from strict because you didn't declare `$d`. And because it comes from strict and not warnings, `no warnings;` has no effect on it. While you can say `no strict 'vars';`, it's much better to just declare $d with my. Perl 6 - second systems done right	[reply] [d/l] [select]
Re^2: How exactly does no work? by PerlOnTheWay (Monk) on Feb 16, 2012 at 11:29 UTC
Why is it NOT fatal when I `print $b;` in `sub a`?	[reply] [d/l] [select]
Re^3: How exactly does no work? by moritz (Cardinal) on Feb 16, 2012 at 11:33 UTC
Because $a and $b are global variables, and thus don't need to be declared. Perl 6 - second systems done right	[reply]
Re^3: How exactly does no work? by choroba (Cardinal) on Feb 16, 2012 at 11:36 UTC
See sort and perlvar. `$a` and `$b` are special variables.	[reply] [d/l] [select]
Re^2: How exactly does no work? by PerlOnTheWay (Monk) on Feb 16, 2012 at 11:37 UTC
Is `no` a run time or compile time thing? And it seems it's only effective in the current block, not in outer or inner block	[reply] [d/l]
Re^3: How exactly does no work? by ww (Archbishop) on Feb 16, 2012 at 11:40 UTC
Minimal reference to the docs -- say `perldoc -f no` -- would put you on the path to answers. See also, as the docs suggest, `use`.	[reply] [d/l] [select]
Re^4: How exactly does no work? by sundialsvc4 (Abbot) on Feb 16, 2012 at 13:49 UTC
Re^5: How exactly does no work? by chromatic (Archbishop) on Feb 17, 2012 at 01:08 UTC
Re^4: How exactly does no work? by PerlOnTheWay (Monk) on Feb 16, 2012 at 11:43 UTC
Re^5: How exactly does no work? by ww (Archbishop) on Feb 16, 2012 at 11:51 UTC
Re^5: How exactly does no work? by rovf (Priest) on Feb 16, 2012 at 13:58 UTC
Re^5: How exactly does no work? by Anonymous Monk on Feb 17, 2012 at 00:39 UTC


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