I suspect you are running into a precedence issue, specifically with the conditional operator (?:) and the assignment operator (=). See perlop.

Personally, though, I found the code hard to read. I'd probably write it something like this: 

$rh = $pkg->{'RPM_HDR'};
$dist = $rh->tag('DISTRIBUTION');

# or $dist = $pkg->{'RPM_HDR'}->tag('DISTRIBUTION');

$pkg->{DIST} = $dist ? $dist : $undef; # $undef or undef?

[download]

Update: Given how you are testing for truth, keep in mind what Perl considers to be a true value (vs a defined value). See True or False? A Quick Reference Guide for examples.

In reply to Re: faulty expression prob by bobf
in thread faulty expression prob by perl-diddler

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