The OP wants

if (!defined($pname) && $pname ne '')

For one, we have

>perl -w -e "print 1 if !defined($pname) && $pname ne ''"
Use of uninitialized value in string ne at -e line 1.
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not defined($pname) && $pname ne ''

if, and only if

! defined($pname) || $pname eq ''

Which looks perfectly reasonable in a test like

if (!defined($pname) || $pname eq '') {
    croak 'We want something real in $pname. Not undef or the empty st
+ring';
}
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