This is an automatically generated page and cannot be edited directly. Text in Composite pages, (URLs starting with 'routine' or 'syntax') can be edited by clicking on the link labeled 'in context', and editing the text there.

Exit this popup by pressing <Escape>, or clicking on X or on the background.

unless
Combined from primary sources listed below.

In Control flow§

See primary documentation in context for unless

When you get sick of typing "if not (X)" you may use unless to invert the sense of a conditional statement. You cannot use else or elsif with unless because that ends up getting confusing. Other than those two differences unless works the same as if:

unless 1 { "1 is false".say }  ; # does not say anything, since 1 is true

unless 1   "1 is false".say    ; # syntax error, missing block

unless 0 { "0 is false".say }  ; # says "0 is false"

unless 42.say and 1 { 43.say } ; # says "42" but does not say "43"
43.say unless 42.say and 0;      # says "42" and then says "43"
43.say unless 42.say and 1;      # says "42" but does not say "43"

$_ = 1; unless 0 { $_.say }           ; # says "1"
$_ = 1; unless 0 -> $_ { $_.say }     ; # says "0"
$_ = 1; unless False -> $a { $a.say } ; # says "False"

my $c = 0; say (1, (unless 0 { $c += 42; 2; }), 3, $c); # says "(1 2 3 42)"
my $d = 0; say (1, (unless 1 { $d += 42; 2; }), 3, $d); # says "(1 3 0)"