How do I use boolean variables in Perl?

Question

I have tried:

$var = false;
$var = FALSE;
$var = False;

None of these work. I get the error message

Bareword "false" not allowed while "strict subs" is in use.

Answer 1

I came across a tutorial which have a well explaination about What values are true and false in Perl. It state that:

Following scalar values are considered false:

• undef - the undefined value
• 0 the number 0, even if you write it as 000 or 0.0
• '' the empty string.
• '0' the string that contains a single 0 digit.

All other scalar values, including the following are true:

• 1 any non-0 number
• ' ' the string with a space in it
• '00' two or more 0 characters in a string
• "0\n" a 0 followed by a newline
• 'true'
• 'false' yes, even the string 'false' evaluates to true.

There is another good tutorial which explain about Perl true and false.

Answer 2

My favourites have always been

use constant FALSE => 1==0;
use constant TRUE => not FALSE;

which is completely independent from the internal representation.