Perl - difference between 'next' and 'continue'?

Question

Quick Perl question: when going through a loop (say a while loop), what is the difference between a next and continue command? I thought both just skip to the next iteration of the loop.

Answer 1

The continue keyword can be used after the block of a loop. The code in the continue block is executed before the next iteration (before the loop condition is evaluated). It does not affect the control-flow.

my $i = 0; when (1) {   print $i, "\n"; } continue {   if ($i < 10) {     $i++;   } else {     last;   } } 

Is almost equivalent to

foreach my $i (0 .. 10){   print $i, "\n"; } 

The continue keyword has another meaning in the given-when construct, Perl's switch-case. After a when block is executed, Perl automatically breaks because most programs do that anyway. If you want to fall through to the next cases the continue has to be used. Here, continue modifies the control flow.

given ("abc") {   when (/z/) {     print qq{Found a "z"\n};     continue;   }   when (/a/) {     print qq{Found a "a"\n};     continue;   }   when (/b/) {     print qq{Found a "b"\n};     continue;   } } 

Will print

Found a "a" Found a "b" 

The next keyword is only available in loops and causes a new iteration incl. re-evaluation of the loop condition. redo jumps to the beginning of a loop block. The loop condition is not evaluated.

Answer 2

Execution of next statment will skip executing rest of the statments in the loop for that pirticular iteration.

Statments in the continue block will execute for each and every iteration, irrespective of loop executed as usual or loop need to terminate the pirticular iteration by encountring the next statment. example with out continue block:

my $x=0; while($x<10) {     if($x%2==0)     {         $x++; #incrementing x for next loop when the condition inside the if is satisfied.         next;     }     print($x."\n");     $x++;  # incrementing x for the next loop  }        

In above example incrementation of x need to be written 2 times. But if we use continue statment which can hold the statments that needed to be executed all the times we can increment x only one time inside continue loop.

my $x=0; while($x<10) {     if($x%2==0)     {         next;     }     print($x."\n"); } continue {         $x++; } 

output in both the cases are 1,3,5,7,9