#!/usr/bin/env perl
use strict;
use warnings;

sub _validate_arguments {
    my ( $first_arg, $second_arg, $arg_count ) = @_;
    croak "Called without arguments." if $arg_count < 1;
    croak "Called with $arg_count arguments. Expected arguments: 1 or 2." if $arg_count > 2;
    croak "The first argument is not defined." if ! defined $first_arg;
    ...
    ...
    carp "The first argument refers to an empty list!" if ! @$first_arg;
    return;
}

sub my_function {
    my ( $first_arg, $second_arg ) = @_;
    _validate_arguments( $first_arg, $second_arg, scalar @_ );
    return if ! @$first_arg;
    ...
    ...
}