Did you declare 'false' and 'true' as constants?

use constant false=>0;
use constant true=>1;

if (false) { print "I do always get printed...\n" }
if (false==true) { print "..and even do I" }
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Otherwise the barewords 'false' and 'true' are treated as strings. Now if you rewrite false==true as  false eq true, the second print will never be executed.