1. 题目
2. 代码与输出
1 # -----------------------------------------------------------# 2 # Source: Learning Perl, chapter10,exercise-1 3 # Date: 2012-01-20 4 # Author: xiaodongrush 5 #-----------------------------------------------------------# 6 use 5.010; 7 $secret_num = int( 1 + rand 100); 8 while(<STDIN>) { 9 chomp; 10 if(/^[ 0- 9]+$/) { # 键入都是数字 11 if( $_ < $secret_num) { 12 say " Too low. Try again. "; 13 } elsif( $_ > $secret_num) { 14 say " Too high. Try again. "; 15 } else { 16 say " You get it. "; 17 last; 18 } 19 } elsif(/^quit$|^ exit$|^\s*$/) { # quit,exit,空白行 20 last; 21 } else { 22 say " Not Vaild Input. Try again "; 23 } 24 } 25 # -----------------------------------------------------------#
1 # -----------------------------------------------------------# 2 # Source: Learning Perl, chapter10,exercise-2 3 # Date: 2012-01-20 4 # Author: xiaodongrush 5 #-----------------------------------------------------------# 6 use 5.010; 7 $secret_num = int( 1 + rand 100); 8 if( @ARGV[ 0] =~ /-debug/i) { 9 say " [DEBUG] The secret num is $secret_num "; 10 } 11 while(<STDIN>) { 12 chomp; 13 if(/^[ 0- 9]+$/) { # 键入都是数字 14 if( $_ < $secret_num) { 15 say " Too low. Try again. "; 16 } elsif( $_ > $secret_num) { 17 say " Too high. Try again. "; 18 } else { 19 say " You get it. "; 20 last; 21 } 22 } elsif(/^quit$|^ exit$|^\s*$/) { # quit,exit,空白行 23 last; 24 } else { 25 say " Not Vaild Input. Try again "; 26 } 27 } 28 # -----------------------------------------------------------#
1 # -----------------------------------------------------------# 2 # Source: Learning Perl, chapter10,exercise-3 3 # Date: 2012-01-20 4 # Author: xiaodongrush 5 #-----------------------------------------------------------# 6 use 5.010; 7 $ENV{ " ZERO "} = 0; 8 $ENV{ " EMPTY "} = ''; 9 $ENV{ " UNDEFINED "} = undef; 10 $max_key_len = 0; 11 $key_len_limit = 10; 12 $value_len_limit = 10; 13 while(( $key, $value) = each %ENV) { 14 if( length( $key) > $key_len_limit) { 15 next; 16 } 17 $max_key_len = $max_key_len > length( $key) ? $max_key_len : length( $key); 18 } 19 say " 1234567890 " x 7; 20 while(( $key, $value) = each %ENV) { 21 if( length( $key) > $key_len_limit || length( $value) > $value_len_limit) { 22 next; 23 } 24 printf " % " . $max_key_len . " s " . " %s\n ", $key, $value // " (undefined) "; 25 } 26 # -----------------------------------------------------------# 27 # 如果$value=''，那么$value || "(undefined)" 返回"(undefined)" 28 # 如果$value=''，那么$value // "(undefined)" 返回''; 29 # 如果$value=undef，$value || "(undefined)" 30 # 和$value // "(undefined)"都返回"(undefined)" 31 #-----------------------------------------------------------#
3. 文件