Perl Breaking out of an If statement

Question

This one just came up: How do I break out of an if statement? I have a long if statement, but there is one situation where I can break out of it early on.

In

Answer 1

I tend to use sequential if-statements based on a "do I continue?" variable instead. Your

if ( $condition1 ) {
  blah, blah, blah;
  if ( not $condition2 ) {
     blah, blah, blah;
     if ( not $condition3 ) {
        blah, blah, blah;
     }
  }
}

can be rearranged to

my $ok = $condition1;
if ($ok) {
  blah, blah, blah;
  $ok = not $condition2;
}
if ($ok) {
  blah, blah, blah;
  $ok = not $condition3;
}
if ($ok) {
  blah, blah, blah;
}

Answer 2

You could put the rest of your if block inside another if statement, like this:

if (some_condition) {
    blah, blah, blah
    if (!$some_other_condition) {
        blah, blah, blah
        ...
    }
}

Answer 3

I was inspired by DVK's answer to play around, and I came up with this variant that works at least on Perl 5.26.1:

for( ; some_condition ; last ) {
    blah, blah, blah
    last if $some_other_condition; # No need to continue...
    blah, blah, blah    
}

Per perlsyn, this is equivalent to:

while (some_condition) {
    blah, blah, blah
    last if $some_other_condition; # No need to continue...
    blah, blah, blah    
} continue {
    last;
}

In a continue block, last has the same effect as if it had been executed in the main loop. Therefore, the loop will execute zero or one times, depending on some_condition.

Tests

perl -E 'my ($cond, $other)=(X, Y); 
         for(;$cond;last) { say "hello"; last if $other; say "goodbye" }'

has the following results, for various X and Y values:

X Y   Prints
-----------------------
0 0   (nothing)
0 1   (nothing)
1 0   hello, goodbye
1 1   hello

Answer 4

Another alternative is to use an anonymous subroutine.
Note: I don't recommend this method because of the added scoping complexity (see note below); it is just for completeness of possible answers.

if( $true_condition ){
   (sub{
       return if $true_condition;
       ...
   })->();
}

Note: any variables declared w/in the routine must use our instead of my if you wish to use them in the rest of the code.

Answer 5

You can use basic block which is subject to last, next and redo, so there is possible break from it.

if ($condition) {EXIT_IF:{

   last EXIT_IF; # break from code block

   print "never get's executed\n";
}}

---

EXIT_IF: {
  if ($condition) {

     last EXIT_IF; # break from code block

     print "never get's executed\n";
  }
}

Answer 6

Keep your while loop so you can use last but also make sure that the loop is executed at most once

my $loop_once = 1;
while ( $loop_once-- and some_condition ) {
    blah, blah, blah
    last if $some_other_condition; # No need to continue...
    blah, blah, blah
    ...
}