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

$_ = "one  two 'three' four\n";
print "\u$_";
print ucfirst;

##</code><code>##

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

$_ = "one  two 'three' four\n";
print "\u$_";
print ucfirst;