my($value) = map { defined() ? $_ : 1 } getConfigValue( "use_foo" );

##</code><code>##

my $value = do { defined(local $_ = getConfigValue( "use_foo" )) ? $_ : 1 }; 

##</code><code>##

sub default {
     my $v = shift;
     return defined $v ? $v : shift;
}

my $value = default(getConfigValue( "use_foo" ), 1);