�� "��" � "��"? � Perl �� , ��, �� , �� . �� �� �� (�� , �� , � �� , �� *). �� (�.�. �� ), �� "�" (�� ), �� "��". �� "��". �� Perl �� ? � ��, �� (� �� ), �� (� �� ) ��, �� "��" � "��". �� .

� # �� "�", �� "��"

1-1 # �� 0, �� "�", �� "��"

1 # �� "I", �� "��"

"" # �� , �� "��"

"1" # �� "" �� "�", �� "��"

"00" # �� "" �� "�", �� "��" (�� , �� )

"0.000" # "��" � �� , ��

undef # �� "", �� "��"

* �� , �� , �� .

�� , �� , �� . �� if:

print "how old are you? ";

$a = <STDIN>;

chomp($a) ;

if ($a < 18) (

print "So, you're not old enough to vote, eh?\n";

( else (

print "Old enough! Cool! So go vote! \n";

$voter++; # count the voters for later )

�� else �� , �� , �� then:

print "how old are you? ";

$a - <STDIN>;

chomp($a) ;

if ($a < 18) (

print "So, you're not old enough to vote, eh?\n";

}

�� "then" �� else, �� "�� , �� ", �� "�� , �� ". � Perl �� unless:

print "how old are you? ";

$a = <STDIN>;

chomp ($a) ;

unless ($a < 18) (

print "Old enough! Cool! So go vote!\n";

$voter++;

�� if �� unless � �� "�� , ��..." (�� unless �� else, �� if.)

�� , �� if �� elsif, ��:

if (�� ) {

��_1_��_��_ ��;

��_2 _��_��_��;

��_ 3_��_��_ �� ;

} elsif (��_��) {

��_1_��_��_��

��_2_��_��_��

��_3_��_��_�� } elsif (��_��) (

��_1_��_��_��

��_2_��_��_��

�� _ 3_��_��_ ��

} else ( -

��__ 1_��_��_��;

��_2_��_���_��/ ��_3_��_��_��;

}

�� . �� -�� , �� , � �� . �� , �� else (�� ). �� else �� , �� . � �� elsif, �� .

�� while/until

�� -�� * (�� ). Perl �� while:

while (��) {

��_1; '

��_2;

��_3;

}

�� while, Perl �� (� �� ��). �� "��" (�� Perl �� ), �� while. �� , �� . �� Perl �� , �� while. ��:

print "how old are you? " ;

$a = <STDIN>;

chomp($a) ;

while ($a > 0) {

print "At one time, you were $a years old.\n";

$a�;

}

�� "�� , �� -�� ", �� "�� ". �� Perl �� . �� while �� until:

until (��) { ��_1;

��_2;

��_3;

} * �� HTML � �� .

�� , �� , �� , �� . ��, �� . Perl �� .

�� , �� . �� , � �� , �� . ��, �� , �� , �� , � �� -�� . �� -��, �� , �� .

�� do {} while/until

�� while/until, �� , �� , �� . �� "��", �� .

�� , � � �� . �� Perl �� do {} while, �� while*, �� , �� .

do (

��_1;

��_2;

��_3;

} while ��;

Perl �� do. �� , �� . �� , �� . �� , �� , � �� .

�� while, �� , �� do {} while �� do {} until. �� , �� . � �� , �� , �� .

$stops = 0;

do (

$stops++;

print "Next stop? " ;

chomp($location = <STDIN>) ;

} until $stops > 5 I I $location eq 'home';

* ��, �� ; �� , �� 9, � �� .

�� for

�� Perl, �� , � �� for, �� for �� Java � �� . �� :

for ( ��_��; ��_�� ,� �� ) (

��_1;

��_2;

��_3;

�� , �� , �� :

�� ;

while (�� ) {

��_1;

��_2;

��_3;

��_��:��;

}

� �� . �� , �� , �� , �� , �� , �� ; �� (� �� ). �� . �� , �� , � �� (�� , �� ). �� Perl �� , �� .

�� 1 �� 10, �� :

for ($i = 1; $i <- 10; $i++) ( print "$i ";

)

�� $i �� 1. �� 10. �� 10, �� (�� print), � �� ($i++), � �� $i �� 2. �� 10, �� , �� 10 � $i �� 11. �� $i �� 10, �� (�� $i �� 11).

�� foreach

�� foreach. �� , �� . �� :

foreach $i (@��) {

��_1;

��_2;

��_3;

}

� �� C-shell, � Perl �� ; �� , �� .

�� foreach:

@� = (1,2,3,4,5);

foreach $b (reverse @a) { print $b;

�� 54321. ��, �� , �� foreach, �� , � �� -��. (�� Perl, �� .)

�� . � �� Perl �� , �� $_. �� , �� $_ �� Perl, �� . (�� , � �� $_, �� .) ��, �� print �� $_, �� , �� , �� :

@� = (1,2,3,4,5);

foreach (reverse @a) {

print ;

}

��, �� $_ �� ? �� , �� $_, �� . �� , �� , �� .

�� , �� , �� , � �� , �� , �� , � �� . �� , ��, �� , �� , �� . ��:

@� = (3,5,7,9) ;

foreach $one (@a) { $one *= 3;

> # @� �� (9,15,21,27)

�� , �� $�� @�.

��

�� .

1. �� , �� "too hot", �� 72 �� (�� ), � � �� "too cold".

2. �� , �� "too hot", �� 75 ��, "too cold" �� 68 �� "just right!" �� 68 �� 75 ��.

3. �� , �� (�� ), �� 999, �� . (�� 999!) ��, �� 1, 2, � � 999, �� 6 (1 + 2 + 3).

4. �� , �� (�� ) � �� , �� reverse. (��, �� <stdin> �� , �� .)

5. �� , �� 0 �� 32 � �� . �� , �� , � �� , �� . (�� , ��

printf "%5g �8�\�", $�, $�

�� $� �� , � $� � �� .

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