Warnings in Perl Eval

I need to hide warnings within eval but the rest of the code should continue to throw warning messages. Here is what I have -

eva开发者_StackOverflow中文版l "\$value = $hash->{key}";

now value of $hash->{key} could be a function call, like:

$hash->{key} = "function(0.01*$another_var)";

The problem comes when $another_var is undef (or ""). The script just craps out with the following message -

Argument "" isn't numeric in multiplication (*) at (eval 1381) line 1.

Any suggestions how I can avoid this? One option i was thinking was to parse the value inside parenthesis and evaluate that first, but its quite complex with the data I am dealing with.

Wrap your code in a no warnings block.

...
{
    no warnings;
    eval "\$value = $hash->{key}";
}
...

You can also disable specific classes of warnings. See perllexwarn for the hierarchy of warning categories and perldiag for the category that any particular warning belongs to.

{
    no warnings qw(uninitialized numeric);
    eval "\$value = $hash->{key}";
}

_{(blah blah blah standard disclaimer that any one who would disable warnings is unfit to get within 25 feet of an adding machine blah blah)}

Are you sure you wouldn't rather do something like:

my $href;
my $somevar = 8;
$href->{foo} = sub { $somevar * 4 };
my $var = $href->{foo}->();

If you're not sure whether $href->{foo} is a scalar, code ref, etc, you can check it with the ref() function, or better, with Scalar::Util::reftype().

Change the hash key to be "function( 0.01 * ($another_var // 0) )"

$another_var // 0 is equivalent to defined($another_var) ? $another_var : 0.