Based on your example, you want to use the GetOpt module. A possible example of what has worked for me in the past, with some default values:

use strict;
(my $cmd = $0) =~ s|^.*/||;   # Program name

# ----------------------------------------
# Handle Command Line options
use Getopt::Std;
&getopts ('d:r:H');

my $DATE;   # $opt_d
my $RCFILE; # $opt_r

# --------------------
# Date
if ($Getopt::Std::opt_d)
{
    $DATE = $Getopt::Std::opt_d;
}
else
{
    $DATE = "TODAY";
}

# --------------------
# Resource File
if ($Getopt::Std::opt_r)
{
    $RCFILE   = $Getopt::Std::opt_r;
}
elsif ( defined($ENV{RCFILE}) )
{
    $RCFILE = "$ENV{RCFILE}";
}
else
{
    warn "ERROR: No RC File Specified\n";    
    $Getopt::Std::opt_H = 1;
}

# --------------------
# Help
if ($Getopt::Std::opt_H)
{
    warn "$cmd:\n";
    warn "    (-m) <milestone>\n";
    warn "    (-r) <rcfile>\n";
    warn "    (-H) <Help>\n";
    exit 1;
}
[download]