Option handling refactored 

• Andrew’s way

use Getopt::Long qw(:config permute);  # allow mixed args.

# Options variables
my $syslog      = 0;
my $logmin      = "notice";
my $dsn         = "dbi:Pg:dbname=weather";
my $dbuser      = "";
my $dbpass      = "";
my $device      = "/dev/ttyUSB0";
my $get_model   = 0;
my $get_version = 0;
my $imperial    = 0;
my $set_time    = 0;
my $get_time    = 0;
my $dump        = undef;
my $backlight   = undef;
my $loopfor     = undef;
my $template    = undef;
my $stream      = undef;
my $interval    = undef;
my $command     = undef;
my $helpmeplease = 0;

GetOptions ('debug!'      => \$debug,
            'syslog!'     => \$syslog,
            'model!'      => \$get_model,
            'version!'    => \$get_version,
            'logmin=s'    => \$logmin,
            'dsn=s'       => \$dsn,
            'dbuser=s'    => \$dbuser,
            'dbpass=s'    => \$dbpass,
            'device=s'    => \$device,
            'imperial'    => \$imperial,
            'gettime!'    => \$get_time,
            'settime'     => \$set_time,
            'backlight=s' => \$backlight,
            'template=s'  => \$template,
            'command=s'   => \$command,
            'loopfor=i'   => \$loopfor,
            'stream=i'    => \$stream,
            'interval=i'  => \$interval,
            'dump:s'      => \$dump,
            'help'        => \$helpmeplease  );

• Grant’s way

use Getopt::Long qw(GetOptions);

my %opt = (
    logmin      => "notice",
    dsn         => "dbi:Pg:dbname=weather",
    device      => "/dev/ttyUSB0",
);

GetOptions(
    \%opt,
    'debug!',
    'syslog!',
    'model!',
    'version!',
    'logmin=s',
    'dsn=s',
    'dbuser=s',
    'dbpass=s',
    'device=s',
    'imperial',
    'gettime!',
    'settime',
    'backlight=s',
    'template=s',
    'command=s',
    'loopfor=i',
    'stream=i',
    'interval=i',
    'dump:s',
    'help',
);