require should work, but you might want to check out something like AppConfig for a much more robust and flexible config file system. 
require '/tmp/b';
print $x;  # 3
# assuming /tmp/b has   $x=3;   in it

[download]
Update: Actually, above was working for me only w/o 'use strict'.

Wasn't going to mention it originally cause it can be BAD, but you can also read in the whole config file and eval, but as recently discussion in the last week or two, this can be BAD.

Update 2: A quick AppConfig example: 
use strict;
use warnings;
use AppConfig;
my $config = AppConfig->new({
            GLOBAL => {
                    DEFAULT  => "<undef>",
                    ARGCOUNT => AppConfig::ARGCOUNT_ONE,
                }
        }, "var1", "var2");
$config->file(\*DATA);
print $config->var1() , "\n";
print $config->var2() , "\n";
__DATA__
var1 = x
var2 = y

[download]

In reply to Re: Include external variables into script by davidrw
in thread Include external variables into script by blackpitch

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.