Question

I am writing a Perl script which does this :

1. Reads the values of the environment variables a to z in a loop.

2. Depending on the value of the environment variables, generates a result file similar to

   a - 1,2,3,4
   b - a,b,c
   c - $234.34,$123.12
   keyword1 %a%
   keyword2 %b%
   keyword3 %c%
   

   The point to note is that all the declarations have to come before the usages.

3. The problem is that for example I read a, and generate this result file

   a - 1,2,3,4
   keyword3 %c%
   

   Now when I read b , I need the result file to look like this

   a - 1,2,3,4
   b - a,b,c
   keyword1 %a%
   keyword2 %b%
   

How should I do this using Perl?

One way I can think of is to generate two different files – one with the declarations and other with the usages, and then concatenate the files at the end of execution of the script.

Is there a better way?

Answer 1

No need for separate files. Accumulate the declarations and usages in two different array variables, @declarations and @usages. After you’ve read all your environment variables and determined the contents of the two arrays, print them:

say for @declarations;
say for @usages;

You might even be able to omit the first array. Once you figure out what a declaration should be, print it out immediately. You only need to accumulate the usages until you know there will be no more declarations.