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How exactly does no work?

by PerlOnTheWay (Scribe)
on Feb 16, 2012 at 11:19 UTC ( #954194=perlquestion: print w/replies, xml ) Need Help??
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();

The first Use of uninitialized value can be fixed by no warnings, but the second is reporting a fatal error,why?

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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.

      Why is it NOT fatal when I print $b; in sub a?

      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

        Minimal reference to the docs -- say perldoc -f no -- would put you on the path to answers. See also, as the docs suggest, use.

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