[原创教程] [连载]《Intermediate Perl》学习笔记

my @input_numbers = (1, 2, 4, 8, 16, 32, 64);
my @bigger_than_10 = grep $_ > 10, @input_numbers;
复制代码

my @end_in_4 = grep /4$/, @input_numbers;
复制代码

my @odd_digit_sum = grep digit_sum_is_odd($_), @input_numbers;

sub digit_sum_is_odd {
    my $input = shift;
    my @digits = split //, $input; # Assume no nondigit characters
    my $sum;
    $sum += $_ for @digits;
    return $sum % 2;
}
复制代码

my @odd_digit_sum = grep {
    my $sum;
    $sum += $_ for split //;
    $sum % 2;
} @input_numbers;
复制代码

my @input_numbers = (1, 2, 4, 8, 16, 32, 64);
my @result = map $_ + 100, @input_numbers;
复制代码

my @result = map { $_, 3 * $_ } @input_numbers;
复制代码

my %hash = map { $_, 1 } @castaways;

my $person = 'Gilligan';
    if( $hash{$person} ) {
    print "$person is a castaway.\n";
}
复制代码

my $average = $total / $count; # divide by zero?
print "okay\n" unless /$match/; # illegal pattern?

open MINNOW, '>', 'ship.txt'
    or die "Can't create 'ship.txt': $!"; # user?defined die?

implement($_) foreach @rescue_scheme; # die inside sub?
复制代码

eval { $average = $total / $count } ;
print "Continuing after error: $@" if $@;
复制代码

my $average = eval { $total / $count };
复制代码

use Try::Tiny;
my $average = try { $total / $count } catch { "NaN" };
复制代码

    eval '$sum = 2 + 2';
    print "The sum is $sum\n";
复制代码

foreach my $operator ( qw(+ ? * /) ) {
    my $result = eval "2 $operator 2";
    print "2 $operator 2 is $result\n";
}
复制代码

print 'The quotient is ', eval '5 /', "\n";
warn $@ if $@;
复制代码

my $bowler;
if( ...some condition... ) {
    $bowler = 'Mary Ann';
}
elsif( ... some condition ... ) {
    $bowler = 'Ginger';
}
else {
    $bowler = 'The Professor';
}
复制代码

my $bowler = do {
    if( ... some condition ... )     { 'Mary Ann' }
    elsif( ... some condition ... )  { 'Ginger' }
    else                             { 'The Professor' }
};
复制代码

$filename = __FILE__;

my $file_contents = do {
    local $/;
    local @ARGV = ( $filename );
    <>;
};

print $file_contents;
复制代码

do "slurp.pl";
复制代码

require List::Util;
复制代码

BEGIN {
    require List::Util;
    List::Util->import( ... );
}
复制代码

require $filename;
复制代码

my %total_bytes;
while (<DATA>) {
    my ($source, $destination, $bytes) = split;
    $total_bytes{$source}{$destination} += $bytes;
}

for my $source (sort keys %total_bytes) {
    for my $destination (sort keys %{ $total_bytes{$source} }) {
        print "$source => $destination:",
        " $total_bytes{$source}{$destination} bytes\n";
    }
    print "\n";
}

__DATA__
professor.hut gilligan.crew.hut 1250
professor.hut lovey.howell.hut 910
thurston.howell.hut lovey.howell.hut 1250
professor.hut lovey.howell.hut 450
ginger.girl.hut professor.hut 1218
ginger.girl.hut maryann.girl.hut 199
复制代码

perl -d bytecounts.pl Loading DB routines from perl5db.pl version 1.37 Editor support available. Enter h or 'h h' for help, or 'perldoc perldebug' for more help. main::(bytecounts.pl:1):        my %total_bytes;    DB<1> s main::(bytecounts.pl:2):        while (<DATA>) {    DB<1> s main::(bytecounts.pl:3):            my ($source, $destination, $bytes) = split;    DB<1> s main::(bytecounts.pl:4):            $total_bytes{$source}{$destination} += $bytes;    DB<1> x $source, $destination, $bytes 0  'professor.hut' 1  'gilligan.crew.hut' 2  1250

DB<8> @a = (1 .. 3);    DB<9> x @a 0  1 1  2 2  3

DB<10> %h = qw/a 1 b 2 c 3/;    DB<12> x \%h 0  HASH(0x2ac9e2c)     'a' => 1     'b' => 2     'c' => 3

DB<31> %h = qw(a b c d e f);    DB<34> x sort keys %h 0  'a' 1  'c' 2  'e'

DB<24> S main   main::BEGIN   main::dumpValue   main::dumpvar   main::test

use Data::Dumper;
print Dumper(\%total_bytes);
复制代码

$VAR1 = {            'thurston.howell.hut' => {                                       'lovey.howell.hut' => 1250                                     },            'ginger.girl.hut' => {                                   'maryann.girl.hut' => 199,                                   'professor.hut' => 1218                                 },            'professor.hut' => {                                 'gilligan.crew.hut' => 1250,                                 'lovey.howell.hut' => 1360                               }          };

use Data::Dumper;
$Data::Dumper::Purity = 1; # 声明打印的数据可能出现自引用的情况
my @data1 = qw(one won);
my @data2 = qw(two too to);
push @data2, \@data1;
push @data1, \@data2;
print Dumper(\@data1, \@data2);
复制代码

$VAR1 = [            'one',            'won',            [              'two',              'too',              'to',              []            ]          ]; $VAR1->[2][3] = $VAR1; $VAR2 = $VAR1->[2];

DB<2> x \@data1, \@data2 0  ARRAY(0x24a4e84)     0  'one'     1  'won'     2  ARRAY(0x47f324)        0  'two'        1  'too'        2  'to'        3  ARRAY(0x24a4e84)           -> REUSED_ADDRESS 1  ARRAY(0x47f324)     -> REUSED_ADDRESS

use Data::Dump qw(dump);
dump( \%total_bytes );
复制代码

{    "ginger.girl.hut"     => { "maryann.girl.hut" => 199, "professor.hut" => > 1218 },    "professor.hut"       => { "gilligan.crew.hut" => 1250, "lovey.howell.hut" > => 1360 },    "thurston.howell.hut" => { "lovey.howell.hut" => 1250 }, }

use Data::Printer;
p( %total_bytes );
复制代码

{      ginger.girl.hut       {          maryann.girl.hut   199,          professor.hut      1218      },      professor.hut         {          gilligan.crew.hut   1250,          lovey.howell.hut    1360      },      thurston.howell.hut   {          lovey.howell.hut   1250      } }