The trick works for me on DWIM Perl 5.14.2:

11:55 >perl -wE "printf qq[%9f\t%.0f\t%2.0f\n], ($_ + 0.5) x 3 for 0 .
+. 10;"
 0.500000       0        1
 1.500000       2        2
 2.500000       2        3
 3.500000       4        4
 4.500000       4        5
 5.500000       6        6
 6.500000       6        7
 7.500000       8        8
 8.500000       8        9
 9.500000       10      10
10.500000       10      11

11:55 >perl -v

This is perl 5, version 14, subversion 2 (v5.14.2) built for MSWin32-x
+86-multi-thread
[download]

Likewise on my 3 Strawberry Perls:

• This is perl, v5.10.1 (*) built for MSWin32-x86-multi-thread
• This is perl 5, version 16, subversion 0 (v5.16.0) built for MSWin32-x86-multi-thread-64int
• This is perl 5, version 18, subversion 0 (v5.18.0) built for MSWin32-x86-multi-thread-64int

I’m running under Windows Vista 32-bit. So it seems that Perl’s printf behaves differently under Windows. No mention of this in perlport or perlwin32, though. Strange.