unfortunately I did not explain right - I am trying to load parameters for "use" from configuration file, using Config::Simple module. The call to Config::Simple will be like

my $cfg = new Config::Simple($configuration_file_from_commandline);

use IO::Socket::Socks::Wrapper (
  Net::POP3 => {
      ProxyAddr => $cfg->param('servername'),
      ProxyPort => $cfg->param('serverport'),
    }
  );
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I assume BEGIN should work for Config::Simple case as well, will try it later. Thanks.