Flame me if it's already told before :-) I couldn't find it.

How about returning a reference to your %temp_vars and adding your new variables like this:

# This would be the return statement of get_page_content
return \%temp_vars;

# And this would be the call:
$new_variables = get_page_content("names");

# $new variables is a reference to your result
@variables{keys %$new_variables}=values %$new_variables;
[download]

Of course this will overwrite all variables that exist in both %tempvars and %variables with the value found in %temp_vars.