nested IFs or multiple condition in single IF - perl - perl

Question

I have some piece of code for multiple conditions in Perl
if (/abc/ && !/def/ && !/ghi/ && jkl) {
#### do something
}
Will every condition will be evaluated at once on every line?
I can prioritize the conditions using nested ifs
if (/abc/){
if (!/def/){
....so on
}

Answer 1

&& short-circuits. It only evaluates its RHS operand if needed. If it's LHS operand returns something false, && will that value.
For example,
use feature qw( say );
sub f1 { say "1"; 1 }
sub f2 { say "2"; 0 }
sub f3 { say "3"; 0 }
sub f4 { say "4"; 0 }
1 if f1() && f2() && f3() && f4();
Output:
1
2
So the following two lines are basically the same:
if (/abc/) { if (!/def/) { ... } }
if (/abc/ && !/def/) { ... }
In fact, if compiles into an and operator, so the above are very close to
(/abc/ and !/def/) and do { ... };
(/abc/ && !/def/) and do { ... };

Answer 2

No.
Think of it like this, if I said
"is the moon bigger than the sun?"
AND "is the pacific bigger than the mediterraan?"
AND "is russia bigger than england?"
AND ... many more AND ....
You could answer "no" very quickly, not having to figure out the answer to anything beyond the first question. It's called "short circuiting"
So in your case, unless an input line matches
/abc/ && !/def/ && !/ghi/
You won't need to evaluate whether it matches /jkl/.