use Data::Dump;
use Getopt::Long;

@ARGV = qw/ --foo --bar=123 --quz=Hello /;
GetOptions(\my %OPTS1, 'foo|f', 'bar|b=i', 'quz|q=s') or die;
dd \%OPTS1;

@ARGV = qw/ -q World /;
GetOptions(\my %OPTS2, 'foo|f', 'bar|b=i', 'quz|q=s') or die;
dd \%OPTS2;

__END__

{ bar => 123, foo => 1, quz => "Hello" }
{ quz => "World" }