The following is the sample code for achieving the above mentioned scenario using require method.
file1.pl

#!/usr/bin/perl -w
use strict;
use warnings;
our $error;

$error = 10;

print "before $error \n";

require 'file2.pl';  # you can use 'do' also

print "after $error \n";
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file2.pl

#!/usr/bin/perl -w
use strict;

our $error = 20;
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output

before 10
after 20
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