人，因思则变。

多行注释：
perl没有多行注释，可以用下面代替：
=pod
代码行;
.
.
.
代码行;
=cut

关于ref函数：
ref EXPR
ref Returns a non-empty string if EXPR is a reference, the empty
string otherwise. If EXPR is not specified, $_ will be used. The
value returned depends on the type of thing the reference is a
reference to. Builtin types include:

SCALAR
ARRAY
HASH
CODE
REF
GLOB
LVALUE

If the referenced object has been blessed into a package, then
that package name is returned instead. You can think of “ref” as
a “typeof” operator.

讲类的段落，比较明了：
Object Construction
All objects are references, but not all references are objects. A reference won’t work as an object unless its referent is specially marked to tell Perl what package it belongs to. The act of marking a referent with a package name–and therefore, its class, since a class is just a package–is known as blessing. You can think of the blessing as turning a reference into an object, although it’s more accurate to say that it turns the reference into an object reference.
阅读全文

看了一个帖子，是说明，如何在awk中使用单引号的，并举了一个例子，原文如下：

awk 中插入单引号需要转义，但是并不是想象中的那么简单。有点周折，发出来和大家共享。

awk ‘{print “INSERT INTO TABLE_NAME (COL1,COL2) VALUES (““’\’’“ $1 “’\’’“ “,“ “’\’’“ $2 “’\’’“ “)“ }’ DATA_FILE >abc.sql

其实，这是比较糟糕的方式，awk的单引号可以用\47 表示，原文中的例子可为：

awk ‘{print “INSERT INTO TABLE_NAME (COL1,COL2) VALUES (\47“$1“\47,\47“$2“\47);“ }‘ DATA_FILE >abc.sql

顺便说一句，原文中所使用的sql语句在“）”后面没有加“；”号，这会有问题的。