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pack EXPR, LIST |
计算该表达式在列表中，包成一个指定的EXPR的二元结构。使用下表中所示的字符格式指定：
每个字符可以被后面可以跟一个数字，指定重复次数的类型被包装的的值。是半字节，字符，或偶数比特，根据该格式。*重复值，为尽可能多的价值保留在LIST中。值可以解压缩与解压缩功能。
例如，A5预期表示五个字母。B32表示，预期32位。为h8表示预期8 nybbles（或4个字节）。P10表示的结构是10个字节长。
包（packed）的版本使用模板来确定它是如何编码的数据列表。
下面是表，它给出在TEMPLATE要使用的值。
| Character | Description |
| a | ASCII character string padded with null characters |
| A | ASCII character string padded with spaces |
| b | String of bits, lowest first |
| B | String of bits, highest first |
| c | A signed character (range usually -128 to 127) |
| C | An unsigned character (usually 8 bits) |
| d | A double-precision floating-point number |
| f | A single-precision floating-point number |
| h | Hexadecimal string, lowest digit first |
| H | Hexadecimal string, highest digit first |
| i | A signed integer |
| I | An unsigned integer |
| l | A signed long integer |
| L | An unsigned long integer |
| n | A short integer in network order |
| N | A long integer in network order |
| p | A pointer to a string |
| s | A signed short integer |
| S | An unsigned short integer |
| u | Convert to uuencode format |
| v | A short integer in VAX (little-endian) order |
| V | A long integer in VAX order |
| x | A null byte |
| X | Indicates "go back one byte" |
| @ | Fill with nulls (ASCII 0) |
试试下面的例子：
#!/usr/bin/perl -w
#by www.gitbook.net
$bits = pack("c", 65);
# prints A, which is ASCII 65.
print "bits are $bits\n";
$bits = pack( "x" );
# $bits is now a null chracter.
print "bits are $bits\n";
$bits = pack( "sai", 255, "T", 30 );
# creates a seven charcter string on most computers'
print "bits are $bits\n";
@array = unpack( "sai", "$bits" );
#Array now contains three elements: 255, T and 30.
print "Array $array[0]\n";
print "Array $array[1]\n";
print "Array $array[2]\n";
这将产生以下这些二进制结果：
bits are A bits are bits are �T Array 255 Array T Array 30
请查看Socket编程会话，看看 pack 函数的使用。