Calling a Variable from another file

[monkfan]

For example I have a hash created with Data::Dumper, stored in a variable $res, in a file called "mydata.pl"

use strict;
#File name: mydata.pl

my $res = {
       # a very big hash reference
       # created with Data::Dumper
       # with a very long processing time
};

And I would like to use that variable for my "main.pl" file.
Can we do that? Just as we call a function. I hope that`s a reasonable question. Thanks beforehand.

[tlm]

I've never actually done what I'm about to propose, so there may be pitfalls I haven't thought of, but assuming that the assignment to my $res is the last executable statement in mydata.pl, I would try something like

my $whatever = do 'mydata.pl';

That should be equivalent to assigning to $whatever the value returned by eval'ing the contents of mydata.pl.

I question the whole approach on design grounds, however. See this thread for some possible alternatives.

[davidrw]

This isn't really the best way to store/pull back stuff, but it is quick & dirty (basically just eval your $res string):

  # storing:
  my $data = ... ; # some big hairy data structure
  open FILE, ">$filename" or die "can't open '$filename': $!";
  print FILE Dumper($data);
  close FILE;

  # retrieving:
  open FILE, "$filename" or die "can't open '$filename': $!";
  my $VAR1;
  eval do{ local $/=undef; <FILE> };
  # your big hairy data structure is in $VAR1 now
  close FILE;

You can also play with the Data::Dumper syntax so that the string had "$data =" instead of "$VAR1 =".

[halley]

The my keyword makes the variable into a private "lexical" variable. Code in other packages cannot refer to it by name.

The our keyword works similarly, but turns the name into a package variable. Then you can refer to it by its package. For example, if declared inside package MyPackageName, then other packages can refer to it as $MyPackageName::res.

I could just tell you that files included with require don't need package names and all of that, but that path leads to madness when your project grows.