scriptname.pl --dir="/dir1/sdir1" --dir="/dir2/sdir2" --file="thisfile.txt"

##</code><code>##

my $params = &GetParameters();
my @dirs = @{ $params->{dir} };
my @file = @{ $params->{file} };
# and so on

sub GetParameters {
  my @allowedParams = qw(file dir);
  die &PrintUsage() unless @ARGV;
  my $params = {}; # shell contain parameters

  foreach (@ARGV){
    my ($key, $val) = split(/\=/, $_, 2); # split up by the first =
 
    # test if $key is a valid parameter
    unless ($key =~ s/^\-\-//) { # must start with --
        die "Error: invalid param $key\n";
    }
    unless ( grep {lc($key) eq lc($_)} @allowedParams){
        die "Error: param $key not allowed\n";
    }
       
    # maybe do some checks if $val is existing
    ....
    # add param to hashreference $params
    push (@{ $params->{$key} }, $val);

  } # for
  return ($params);
} # GetParameters