Use the ?: operator:

my $value=defined(getConfigValue("use_foo""))?getConfigValue("use_foo"
+):1;
[download]

But your solution does basically the same and is not messy IMO. You could rewrite it as such:

my $value = getConfigValue( "use_foo");
$value=1 unless defined $value;
[download]

Which looks a bit better (and is more Perlish).

Please not that code provided is untested.

CU
Robartes-