# single arg, used for simple and dirty
sub foo {
    my $arg = shift;
}

# more flexible, I've been using this more frequently for complex subs
sub bar {
    my ($arg1, $arg2, @optionals) = @_;
}

# I want more sophisticated argument handling for optional args, so I pass a hash reference containing all the arguments in predefined keys
sub bletch {
    my $href = shift;
    # will warn me if $href->{hello_sub} is not defined
    print 'hi!' if $href->{hello_sub};
}

##</code><code>##

# processes arguments passed to subroutine in hashref
# returns hash
sub sub_opts {
	my $href = shift;
	
	error("bad options hashref: $href") if ref($href) ne 'HASH';
		
	# get all options to return if they exist
	my %hash = map {$_ => exists $href->{$_} ? $href->{$_} : 0} keys %{$href};
	return %hash;
}

# implemented like:
sub foobie {
    my %opts = sub_opts(shift);
    # won't warn me if $opts{hello_sub} doesn't exist, just treats it as false
    print 'hi!' if $opts{hello_sub};
}