{"id":19,"date":"2009-09-14T13:58:00","date_gmt":"2009-09-14T17:58:00","guid":{"rendered":"http:\/\/galencharlton.com\/blog\/?p=19"},"modified":"2009-09-14T13:58:00","modified_gmt":"2009-09-14T17:58:00","slug":"what-is-truth","status":"publish","type":"post","link":"https:\/\/galencharlton.com\/blog\/2009\/09\/what-is-truth\/","title":{"rendered":"What is truth?"},"content":{"rendered":"

Not paying close attention to Perl’s definition of truth can sometimes lead to subtle bugs. Consider a simple scalar $x<\/code> that should contain a string exactly one character wide. If the original value of $x<\/code> can be undefined and you want to make sure it has a default value of a single space, do not<\/em> do the following:
\n
\n$x ||= ' ';
\n<\/code><\/p>\n

Why not? If $x<\/code> starts off as ‘0’, a permitted value, this line will change it to ' '<\/code>. Instead, do this
\n
\n$x = ' ' unless defined $x;
\n<\/code><\/p>\n

Remember, 0<\/code>, '0'<\/code>, ''<\/code>, and undef<\/code> all<\/em> evaluate to Perl’s notion of false.<\/p>\n

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