如何重新定义内置的Perl函数？

use strict;
use warnings;

# 重新定义内置的uc函数
sub CORE::GLOBAL::uc {
    my ($scalar) = @_;
    return lc($scalar);
}

# 测试重新定义的uc函数
my $string = "HeLLo, WoRlD!";
print "Original string: $string\n";
print "New string: " . uc($string) . "\n";

Original string: HeLLo, WoRlD!
New string: hello, world!