Guide Practice of Perl

#!/usr/bin/perl
use strict;
use warnings;

#This is a practice of perl, as which shows with below perl code...codes.

print "Hello, world!\n";

my $animal = "camel\n";
my $answer = 42;

printf $animal;
print "The animal is $animal\n";
print "The square of $answer is ", $answer * $answer, "\n";

print;

my @test = ("t1", "t4", "t3");
print $test[0], $test[1], $test[$#test], "\n";
print "@test\n";

my @sorted = sort @test;
print "@sorted\n";

my @backwards = reverse @test;
print "@backwards\n";

my %fcolor = (
  apple => "red",
  banana => "yellow",
);

my $apple = $fcolor{"apple"};
print "apple color is $apple. \n";

my @fruits = keys %fcolor;
my @colors = values %fcolor;
print "list fruits: @fruits. \n";
print "list colors: @colors. \n";

my $variables = {
  scalar => {
    desc => "sigle item",
    sigil => '$',
  },

  array => {
    desc => "ordered list of items",
    sigil => '@',
  },

  hash => {
    desc => "key/value pairs",
    sigil => '%',
  },

};
print "scalar begin with a $variables->{'scalar'}->{'sigil'}. \n";
print "array begin with a $variables->{'array'}->{'sigil'}. \n";
print "hash begin with a $variables->{'hash'}->{'sigil'}. \n";

my $x = "x";
my $some_condition = 1;
if ($some_condition) {
  my $y = "y";
  print $x;
  print $y;
}
print $x;
#print $y;
print "\n";

print "unless condition.\n" unless(0);

until (1) {
  print "while condition.\n";
};

foreach (@test) {
  print "array element is $_\n";
}

print "array element is $test[$_]\n" foreach 0 .. $#test;

foreach my $key (keys %fcolor) {
  print "The value of $key is $fcolor{$key} \n";
}

my $a = 1;
$a += 1;
print "$a\n";
$a -= 1;
print "$a\n";
$a .= "x";
print "$a\n";

open(my $in, "<", "input.txt") or die "can't open input.txt: $!\n";

#my $line = <$in>;
#my @lines = <$in>;
#print "$line";
#print "@lines";

print stderr "stderr test.\n";

while (<$in>) {
  print "$_";
}
print "\n";

close $in or die "$in: $!";

open(my $out, ">", "output.txt") or die "can not open output.txt. \n";
print $out "hello world!\nWrite this info into output.txt. \n";
close $out or die "$out: $!";

=pod
while(<>) {
    next if /^$/;
    last if (/q/);
  print;
}
=cut

my $email = "hk.mars\@aol.com";

if ($email =~ /([^@]+)@(.+)/) {
  print "username is $1 \n";
  print "hostname is $2 \n";
}

#subroutines
sub loger {
  my $logmessage = shift;

  open my $logfile, ">>", "my.log" or die "can not open my.log.$!";
  print $logfile $logmessage;
}

loger("hello loger! \n");

sub square {
  my $num = shift;
  my $sq;

  $sq = $num * $num;
  return $sq;
}

my $sq = square(5);
print "the square result of 5 is $sq \n";

#OO Perl

#Using Perl modules

#The end of this practice, let's start to write project...now...

Write above perl codes into "e1.pl" file or any name as you want, and executes it on the shell, below is the result shown:

Yet, perl is so easy as C. I am so expected to start  the web project using perl. I guess only need one week to hack a website done.

Mars