Documentation improvement

Hi.

It is a bit ambiguous where pragma is limited:

On the `warnings` [page](https://perldoc.perl.org/warnings.html)

>This means that the scope of the warning pragma is limited to the enclosing block

but on the `strict` [page](https://perldoc.perl.org/strict.html)

>The effect of this pragma is limited to the current file or scope block

And after reading `my` [page](https://perldoc.perl.org/functions/my.html) it is more ambiguous about limitation for pragma:

>A my declares the listed variables to be local (lexically) to the enclosing block, file, or eval


if pragma is limited to 'eval' too it should be explicitly documented on corresponding pages

• Documentation improvement by KES
• Re: Documentation improvement by Tom Hukins