- Prison Code Breaker Diary -

I'm talking about the conditional statement IF.
Here is the definition:

IF (exp) {
   (statement)
}

Try this example:

$age = 23; 
if ( $age == 23 ) {
   print "I am 23 years-old", '\n'
}

Certainly perl evaluates the expression is TRUE since $age is assigned to the value '23'.
How about this case:

if ( $age = 23 ) {
   print "I am 23 years-old", '\n'
}

Still you've got the result printed. But how do you explain what perl does to this evaluation?

1. First, $age is assigned to value '23'.
2. The expression is evaluted whether it is TRUE or FALSE, which means, $age is ZERO or non-ZERO. So, it's TRUE right here because '23' is definitely not '0'.
3. Statement 'print' is called.

Rewrite the explanation into the code itself:

$age = 23;
if ($age) {
   print "I am 23 years-old", '\n'
} 

If u try with constants assignment, u'll get error

if ( 20 = 55 ) {    
    print "is it ok?", '\n'
}

Same results but different operators mean differences.

I'm mentioning about the '=' and the '==' operators with different means, applied to all logical cases.