Re: warnings pragma anomaly

[muba]

Another place where using 1 in void context is commonplace is near/at the end of modules. When use Foo loads Foo.pm, then the last expression evaluated inside Foo.pm better be a true value, to signal that the module loaded succesfully. That's why you usually see the line

1;

near or at the end of a .pm file. Because 1 evaluates to a true value, but is special-cased not to raise a warning.

[choroba]

As the return value of this expression is returned and checked for truthness, it's not used in a void context. Moreover, you can use any true value at the end of a module, and you won't get any warnings. See also Acme::ReturnValue.

Update: You can check the generated lists here.

[BrowserUk]

As the return value of this expression is returned and checked for truthness, it's not used in a void context.

Are you sure about that? If you end a package with just: 1; no warning is produced; but if you end it with just: 42;:

C:\test>perl -Mstrict -w
package x;

sub f{ 1 }

42;
^Z
Useless use of a constant in void context at - line 5.

Although it is returned and checked at runtime; at the point of parsing it is in a void context.

And you can't avoid that by prefixing a return statement either:

C:\test>perl -Mstrict -w
package x;
sub f{ 1 }
return 42;
^Z
Can't return outside a subroutine at - line 3.

[choroba]

I usually don't run modules, I use them. No warning is produced in such situations.