perl-PerlX-Maybe

Return a pair only if they are both defined

Moose classes (and some other classes) distinguish between an attribute being unset and the attribute being set to undef. Supplying a constructor arguments like this: my $bob = Person->new( name => $name, age => $age, ); Will result in the 'name' and 'age' attributes possibly being set to undef (if the corresponding '$name' and '$age' variables are not defined), which may violate the Person class' type constraints. (Note: if you are the _author_ of the class in question, you can solve this using MooseX::UndefTolerant. However, some of us are stuck using non-UndefTolerant classes written by third parties.) To ensure that the Person constructor does not try to set a name or age at all when they are undefined, ugly looking code like this is often used: my $bob = Person->new( defined $name ? (name => $name) : (), defined $age ? (age => $age) : (), ); or: my $bob = Person->new( (name => $name) x!!(defined $name), (age => $age) x!!(defined $age), ); A slightly more elegant solution is the 'maybe' function.