Question

I am cleaning my Perl code for production release and came across a weird warning in the Apache error log.

It says:

[Thu Nov 5 15:19:02 2009] Clouds.pm: Use of uninitialized value $name in substitution (s///) at /home/mike/workspace/olefa/mod-bin/OSA/Clouds.pm line 404.

The relevant code is here:

my $name         = shift @_;
my $name_options = shift @_;

$name_options = $name_options eq 'unique'     ? 'u'
              : $name_options eq 'overwrite'  ? 'o'
              : $name_options eq 'enumerate'  ? 'e'
              : $name_options =~ m/^(?:u|o|e)$/ ? $name_options
              : q();

if ($name_options ne 'e') {
   $name =~ s/ /_/g;
}

So, why the warning of an uninitialized variable as it is clearly initialized?

Answer 1

The warning simply means that $name was never filled with a value, and you tried doing a substitution operation (s///) on it. The default value of a variable is undefined (undef).

Looking back through your script, $name gets its value from @_. This means either @_ was empty, or had its first value as undef.