But i want to assign those values to some scalar variables which i will use in my program later for another use. If there is any alternative please suggest

Change the rest of the program so it doesn't expect the values to appear in scalar variables. Really. Your code will be much easier to understand if it says this:

my $first = $config_values{first};
open my $file, $first;
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rather than just blithely saying the second line and leaving the poor reader to figure out how $first got its value.