1 #-----------------------------------------------------------#
 2 # Source: Learning Perl, chapter2
 3 # Date:   2012-01-12
 4 # Author: xiaodongrush
 5 #-----------------------------------------------------------#
 6 #                          code-1                           #
 7 #-----------------------------------------------------------#
 8 $split = "-------------------------------------------------";
 9 $code1 = 'print 12.5 * 2 * 3.14_15926_54 . "\n";';
10 print "code-1\n" . $code1 . "\n" . $split;
11 #-----------------------------------------------------------#
12 #                          execute-1                        #
13 #-----------------------------------------------------------#
14 print "\nexecute-1\n";
15 print 12.5 * 2 * 3.14_15926_54 . "\n";
16 #-----------------------------------------------------------#
17 #                          code-2                           #
18 #-----------------------------------------------------------#
19 $code2 = 'print "input r\n";'                       . "\n" . 
20          'chomp($r = <STDIN>);'                     . "\n" . 
21          'print $r * 2 * 3.14_15926_54 . "\n";';
22 print $split . "\ncode-2\n" . $code2 . "\n" . $split;
23 #-----------------------------------------------------------#
24 #                          execute-2                        #
25 #-----------------------------------------------------------#
26 print "\nexecute-2\n";
27 print "input r\n";
28 chomp($r = <STDIN>);
29 print $r * 2 * 3.14_15926_54 . "\n";
30 #-----------------------------------------------------------#
31 #                          code-3                           #
32 #-----------------------------------------------------------#
33 $code3 = 'print "input r\n";'                      . "\n" . 
34          'chomp($r = <STDIN>);'                    . "\n" .
35          'if ($r < 0) {'                           . "\n" . 
36          '  print 0;'                              . "\n" .
37          '} else { '                               . "\n" .
38          '  print $r * 2 * 3.14_15926_54 . "\n";'  . "\n" .
39          '}';
40 print $split . "\ncode-3\n" . $code3 . "\n" . $split;
41 #-----------------------------------------------------------#
42 #                          execute-3                        #
43 #-----------------------------------------------------------#
44 print "\nexecute-3\n";
45 print "input r\n";
46 chomp($r = <STDIN>);
47 if ($r < 0) {
48   print 0; 
49 } else {
50   print $r * 2 * 3.14_15926_54 . "\n";
51 }
52 #-----------------------------------------------------------#
53 #                          code-4                           #
54 #-----------------------------------------------------------#
55 $code4 = 'print "input x\n";'        . "\n" .
56          'chomp($x = <STDIN>);'      . "\n" .
57          'print "input y\n";'        . "\n" .
58          'chomp($y = <STDIN>);'      . "\n" .
59          'print $x . " * " . $y . " = " . ($x * $y) . "\n";';
60 print $split . "\ncode-4\n" . $code4 . "\n" . $split;
61 #-----------------------------------------------------------#
62 #                          execute-4                        #
63 #-----------------------------------------------------------#
64 print "\nexecute-4\n";
65 print "input x\n";
66 chomp($x = <STDIN>);
67 print "input y\n";
68 chomp($y = <STDIN>);
69 print $x . " * " . $y . " = " . ($x * $y) . "\n";
70 #-----------------------------------------------------------#
71 #                          code-5                           #
72 #-----------------------------------------------------------#
73 $code5 = 'print "input str\n";'      . "\n" .
74          'chomp($str=<STDIN>);'      . "\n" .
75          'print "input num\n";'      . "\n" .
76          'chomp($num=<STDIN>);'      . "\n" .
77          'print $str x $num . "\n";';
78 print $split . "\ncode-5\n" . $code5 . "\n" . $split;
79 #-----------------------------------------------------------#
80 #                          execute-5                        #
81 #-----------------------------------------------------------#
82 print "\nexecute-5\n";
83 print "input str\n";
84 chomp($str=<STDIN>);
85 print "input num\n";
86 chomp($num=<STDIN>);
87 print $str x $num . "\n";
88 #-----------------------------------------------------------#
89 print "END!!!";
90 <STDIN>
91 #-----------------------------------------------------------#
92 # 总结
93 # 1. 当作数字使用的字符串，可以不用chomp
94 # 2. if-else必须要用"{}"
95 # 3. 字符串重复操作，用x
96 #-----------------------------------------------------------#