Подпрограммы и аргументы

sub bump { $_[0]++ }
my $x = 4;
bump($x);
say $x;

sub add :prototype($$) {
    return $_[0] + $_[1];
}
say add 2, 3 * 4;

sub f { my ($x) = @_; return $x, $x + 1 }
my $v = f(5);
say $v;

sub create { my %arg = @_; say $arg{name} }
create(name => 'Ada', active => 1);

sub normalize { for (@_) { s/^\s+|\s+$//g } }

sub takes_array :prototype(@) {
    return scalar @_;
}
my @items = (1, 2);
say takes_array(@items);

sub find { return; }
my @x = find();
my $x = find();

sub create { my %arg = @_; }
create(name => 'Ada', 1);

sub normalize { return map { my $v = $_; $v =~ s/^\s+|\s+$//g; $v } @_ }

sub add { my ($a, $b) = @_; die 'arity' unless @_ == 2; return $a + $b }

sub find_one {
    my ($rows, $wanted) = @_;
    for my $row (@$rows) {
        return $row if $row->{id} eq $wanted;
    }
    return undef;
}

sub find_all {
    my ($rows, $wanted) = @_;
    return grep { $_->{id} eq $wanted } @$rows;
}

sub create { my %arg = @_; die 'name' unless exists $arg{name}; die 'unknown' if grep { $_ ne 'name' && $_ ne 'active' } keys %arg; }