BEGIN {
  *CORE::GLOBAL::ucfirst = sub {
     join ' ', map CORE::ucfirst, split / /, defined $_[0] ? $_[0] : $_;
  }
}

$_ = "I shouldn't be printing this, but I am anyway.";
my $var = undef;
print ucfirst $var;

##</code><code>##

BEGIN {
  *CORE::GLOBAL::ucfirst = sub {
     join ' ', map CORE::ucfirst, split / /, @_ ? $_[0] : $_;
  }
}