... something in your @HR is coming up as an undef.

I was going to write that a simple empty array could also produce an "... uninitialized value in printf ..." warning, but warnings apparently got a little bit smarter in version 5.12: 

c:\@Work\Perl>perl -wMstrict -le
"print 'perl version ', $];
 ;;
 my @HR;
 ;;
 printf qq{A: %s \n}, @HR;
 ;;
 ++$#HR;
 printf qq{B: %s \n}, @HR;
"
perl version 5.008009
Use of uninitialized value in printf at -e line 1.
A:
Use of uninitialized value in printf at -e line 1.
B:

perl version 5.010001
Use of uninitialized value in printf at -e line 1.
A:
Use of uninitialized value in printf at -e line 1.
B:

perl version 5.012003
Missing argument in printf at -e line 1.
A:
Use of uninitialized value in printf at -e line 1.
B:

perl version 5.014004
Missing argument in printf at -e line 1.
A:
Use of uninitialized value in printf at -e line 1.
B:

[download]
(See 'Missing argument in %s' in perldiag in version 5.12 and after.)

Update: Posted this reply before seeing other, closely related replies: this from Monk::Thomas and this from hippo.

Give a man a fish:  <%-{-{-{-<

In reply to Re^2: Troubleshooting perl runtime errors by AnomalousMonk
in thread Troubleshooting perl runtime errors by lvirden

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