sub checkForDirectory (&) {
  my $cond = shift;

  ## ...
}

## ...
my $result = checkForDirectory { ! -d $_[0] };
my $also_result = checkForDirectory sub { -M $_[0] > 2 }

##</code><code>##

my $predicate = sub { $_[0] =~ /^\d{4}-\d{2}-\d{2}/ };
my $other_result = &checkForDirectory( $predicate );