Use of uninitialized value in pattern match (m//)

[anaconda_wly]

I don't know why below error message(I add it in the comment)

 
{
    package packageA
    my %hash_map = (
      "name" => "path",
      ......,
    );
    sub new{
      ........
    }
    sub get{
      my $class = shift;
      my $componentName = @_;
    
      my $path = $component_path{$componentName};
#error:
#Use of uninitialized value $path in pattern match (m//) at below...
        if($path =~ m/HKEY_LOCAL_MACHINE/){
            dosomthing;          
        }
    }
}

[choroba]

The key $componentName does not exist in %component_path or is assigned an undef. The reason might be you assign the number of subroutine arguments to $componentName: instead of

my $componentName = @_;

you probably meant

my ($componentName) = @_; # list context

or

my $componentName = $_[0];

or even

my $componentName = shift;

[anaconda_wly]

Yes, you both are right. I missed the componentName's value when called. Thanks!

[Corion]

What is the value of $componentName, and what are the values of %component_path? The error message suggests that $component_path{ $componentName } is uninitialized, which likely means that the value of $componentName is not what you expect it to be.

I recommend printing out the value of $componentName.

[space_monk]

AFAICT, the hash $component_path is not defined in the example you gave, so $path in the get() method will also be undefined, so you are trying to pattern match against an undefined variable.