# 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};
}