my @extList;
push @extList, $_ for @ARGV;

##</code><code>##

use Getopt::long;
my @extList;
my $root;
GetOptions(
  'ext=s' => \@extList,
  'root|dir=s' => \$root,
);
@extList = @extList
  ? map { split /,/ } @extList; # in case of --ext foo,bar
  : qw( pl pm );
$root ||= '.';