Question

This snippet of Perl code in my program is giving the wrong result.

$condition ? $a = 2 : $a = 3 ; print $a; 

No matter what the value of $condition is, the output is always 3, how come?

Answer 1

This is explained in the Perl documentation.

Because of Perl operator precedence the statement is being parsed as

($condition ? $a= 2 : $a ) = 3 ; 

Because the ?: operator produces an assignable result, 3 is assigned to the result of the condition.

When $condition is true this means ($a=2)=3 giving $a=3

When $condition is false this means ($a)=3 giving $a=3

The correct way to write this is

$a = ( $condition ? 2 : 3 ); print $a; 

We got bitten by this at work, so I am posting here hoping others will find it useful.