You should add a check after the line my $password=.... The quickest fix I can think of is:

my $password = $p->param('password') || '';
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That is, if the password is defined, use it, otherwise use an empty string.

Another word on your string testing if ($name ne " "), it's better written as:

if ( ($name !~ /^\s*$/) && ($password !~ /^\s*$/) ... )
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Otherwise if $name or $password contains two empty spaces your eq testing will fail.