How to replace the predefined variable which is set after the decleration

[yash0101]

I have a hash , and in the value part of that (which is a string , So that variable interpolation can happen) i have used a variable .
Now later in the program i set this variable and try to substitute the value of it in the value of hash but it is returning null;

%Hash=('add'=> " test  $type ");
$type = 1000;

print " $Hash{$type};";

[numberwhun]

I have a hash , and in the value part of that (which is a string , So that variable interpolation can happen) i have used a variable .
Now later in the program i set this variable and try to substitute the value of it in the value of hash but it is returning null;

%Hash=('add'=> " test  $type ");
$type = 1000;

print " $Hash{$type};";

You have to define the variable $type before you use it somewhere, otherwise, the place where its used will be filled with a null value.

My suggestion is that you add the following to the beginning of your script:

use strict;
use warnings;

If you had them in place, you would have seen the following output to your screen:

Global symbol "%Hash" requires explicit package name at hashtest.pl line 20.
Global symbol "$type" requires explicit package name at hashtest.pl line 20.
Global symbol "$type" requires explicit package name at hashtest.pl line 21.
Global symbol "%Hash" requires explicit package name at hashtest.pl line 23.
Global symbol "$type" requires explicit package name at hashtest.pl line 23.
Execution of hashtest.pl aborted due to compilation errors.

Also, this line:

print " $Hash{$type};";

is not correct. The first semi-colon needs to be rmoved so it looks like this:

print " $Hash{$type}";

Another issue is that $type is the value and the way you are referencing it is as if it were a key, so you will always get the following error:

Use of uninitialized value within %Hash in concatenation (.) or string at hashtest.pl line 24.

To have this code work the way you expect it, you will have to have it as follows:

use strict;
use warnings;


# Variables
my $type = "1000";
my %Hash=('add' => " test  $type ");


#print " $Hash{$type}";
print("$Hash{add}");

I hope this helps.

Regards,

Jeff

[yash0101]

Thanks jeff ,
and print " $Hash{$type};"; was a typing mistake.

And what actually my problem is that i want to make the code more generic and to do that i use the variable inside the hash and i replace that variable at the runtime.

So, because of this reason i cant hard code the $type before the hash.

What i want is something like if i can some how refer to the variable and can change the value stored in that variable at the runtime .

Anyways thansk for the reply.
:)

[KevinADC]

You can change the value of a variable, but not when it is used in a string. When you put a variable in a string its value replaces the variable, and then perl builds the string. The variable is not stored in the string only its value.

[yash0101]

Thanks KevinADC for the reply..