As others have said, check out the do, require, and use documentation. I sometimes just make the config file a simple anonymous hash and then grab it via require()'s return value:

# example program:

#!/usr/bin/perl -w
use strict;
my $config = require("config.txt");
print "$config->{var1} $config->{var2}\n";
__END__


# and here's config.txt:

{
    var1 => 'Hello',
    var2 => 'World',
}
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