perl6/doc/lib/Block
doc src
(title) class Block
class Block is Code { }
A Block is a code object meant for small-scale code reuse. A block is
created syntactically by a list of statements enclosed in curly brackets.
Without an explicit signature or placeholder arguments, a block has $_
as a positional argument
my $block = { uc $_; };
say $block.WHAT; # Block
say $block('hello'); # HELLO
A block can have a signature between < - >> or < <- >> and the block:
my $add = -> $a, $b { $a + $b };
say $add(38, 4); # 42
If the signature is introduced with < <- >>, then the parameters are marked
as rw by default:
my $swap = <-> $a, $b { ($a, $b) = ($b, $a) };
my ($a, $b) = (2, 4);
$swap($a, $b);
say $a; # 4
Blocks that aren't of type Routine (which is a subclass of Block ) are
transparent to L<return>.
sub f() {
say <a b c>.map: { return 42 };
# ^^^^^^ exits &f, not just the block
}
Bare blocks in sink context are automatically executed:
say 1;
{
say 2; # executed directly, not a Block object
}
say 3;
