I would much agree on the remarks made by other monks, to use a hash for your config vars is a much cleaner and safer approach.

Having said that, your idea of using an eval can work as per below example. Just keep in mind that:

• eval runs as a nested block, therefore any variables declared within eval are lost once eval is done. Hence you you need to declare your variables before using them in the eval.
• make sure that your eval cannot be abused thru evil data in a configfile. So check all input before you use it in eval, make sure to single-quote string so that they do not get interpreted, etc etc.

#!/usr/bin/perl
use warnings;
use strict;

my @accepted_vars = qw( myvar1 myvar2 );
my $myvar1; # must declare variable beforehand!
my $myvar2;

my @lines = <DATA>;
chomp @lines;

foreach (@lines) {
    if  (  /^\s*(.*?)\s*=\s*(.*)/  &&
          grep $1 eq $_ , @accepted_vars
        ) {
        eval '$'."$1 = '$2'";
        warn "eval failed: $@\n" if $@;
        }
    else {
        warn "Illegal config var '$1'\n";
        }
    }

print "myvar1 = '$myvar1'\n",
      "myvar2 = '$myvar2'\n";

__DATA__
myvar1 = foo
myvar2 = bar
evil_var = foo
[download]

Output from program is:

Illegal config var 'evil_var'
myvar1 = 'foo'
myvar2 = 'bar'
[download]