sub process_variables {
    my ( $value, $remove_undef ) = @_;

    $value =~ s/ (?<! \\ ) \$ \{ ( .*? ) \} /
        defined $variable{ $1 }
            ? $variable{ $1 }
            : defined $remove_undef && $remove_undef
                # for if statements, any variable that is not defined,
                # we simple convert to 0
                ? '0'
                # This could be an option that is used later, save
                # it so we don't warn if this option is not one of
                # ktests options. And put back the origin piece.
                : ( $used_options{ $1 } = 1 and "\${$1}" )
        /exg;

    return $value;
    }