Perl Loops

Loops are used to execute a set of statements repeatedly until a particular condition is satisfied.
Perl provides following ways for executing the loops.

 1) While:
A while loop is a control flow statement that allows code to be executed repeatedly based on a given Boolean condition.  
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$a=1;

#While loop
while($a<10){
 print "$a ";
 $a=$a+1;
}
Output: 1 2 3 4 5 6 7 8 9

 2) Do while: 
do while loop is similar to while loop with only difference that it checks for condition after executing the statements. 
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$a=11;

#Do while loop
do{
 print "$a ";
 $a=$a+1;
}while($a<20);
Output: 11 12 13 14 15 16 17 18 19

 3) Until:
Repeats the statements inside its body till its condition is false. 
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$a=0;

#until loop
#Repeats the statements inside its body till its condition is false
until ($a>5){  
 print "$a ";
 $a = $a+1;
}
Output: 0 1 2 3 4 5 

 4) for: 
for statement consumes the initialization, condition and increment/decrement in one line thereby providing a shorter, easy to debug structure of looping. 
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#For loop
for ($a = 1 ; $a <= 5 ; $a ++ ){
     print ( "Hello " ) ;
}
Output: Hello Hello Hello Hello Hello

 5) for-each:
A foreach loop is used to iterate over each element of a list. 
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@list = (10, 20, 30, 40, 50);
#For each loop
foreach $a (@list) {
   print "value of a: $a\n";
}
Output: 
value of a: 10
value of a: 20
value of a: 30
value of a: 40
value of a: 50
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