Course of Raku / Essentials / Control flow essentials / Conditional checks

Using unless

All Boolean conditions can be easily negated with the ! operator. However, in some cases, an explicit negation makes the expression heavier and less readable. In these cases, unless can be a friend.

The unless block is executed when its condition is False.

my $broken = False;

# ...Something can set $broken to True here...
    
unless $broken {
    say "Don’t worry!";
    say "Be happy!";
}

Compare the two variants of the same program:

With if and negation:

if !$broken { . . . }

With unless:

unless $broken { . . . }

Having the alternatives, you can always choose what feels better to you in the current situation.

Notice that unless cannot be followed by an else or elsif block. In this case, the only way is to use if.

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← Quiz: if, elsif, and else   |   if and unless as statement modifiers →

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