The use of control structures in Perl

If control structure

Chomp (My $a = <STDIN>);  User input variable $a value
if ($a > 0) {  If $a is greater than 0 executes command
        print "$a is larger than 0\n"; 
} 
elsif ($a = = 0) {  if $a equals 0 then execute command
        print "$a equals 0\n"; 
} 
else{  If $a is less than 0 execute command
        print "$a is smaller than 0\n"; 
}

Unless control structure in contrast to if action, to execute a command when judged false

Chomp (My $a = <STDIN>); 
Unless ($a > 0) { 
        print "$a is not larger than 0\n"; 
}

While control structure

$b = 0;  Assign a value of variable $b 0
while ($b <) {  when $b is less than 20 o'clock execute the command in the
        loop $b + +; 
        Say "$b"; 
}

See more highlights of this column: http://www.bianceng.cnhttp://www.bianceng.cn/Programming/extra/

while (<>) {  always lets the user input string
        if (/fred/) {  Print if the string containing "Fred" is entered, print is not printed
                ; 
        } 
}

Until control structure, which, contrary to the while function, executes the loop when the judgment is false

Until (0) { 
        print ' test '; 
}

foreach Control structure

foreach (1..10) {  The list is a value from 1 to 10 and loops print
        "$_\n"; 
}

foreach $str (Qw/hello bye the you/) {  loops through the list of strings to print
        "$STR \ n"; 
}

For control structure, similar to foreach

For ($i =10 $i >0; $i-) {  variable $i cycles from 10 to 1 and prints print
        "$i \ n"; 
}

This article is from the "Strive for" blog, please be sure to keep this source http://carllai.blog.51cto.com/1664997/1186224