do is, essentially, a file-slup + eval all in one. Try the following:

data.txt
--------
$foo = "Hello, World";

data.pl
-------
#!/usr/local/bin/perl

use 5.6.0;

use strict;

our $foo;

do 'data.txt';

print $foo, $/;

__END__
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Note that this will only work with non-lexical variables. If you change to my $foo;, this will not work, due to the lexical scoping of my. Before 5.6.0, this trick is accomplished with use vars qw/$foo/; instead of our $foo;

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