perl 5.14 and up will break some of well known programs! Think twice (test thrice) before use it!

Seems that at some point someone thought that a qw() in a for loop should be surrounded by parents (qw()).
Lines like

$  perl -e 'foreach $x qw(1 2 3){print $x}'
Use of qw(...) as parentheses is deprecated at -e line 1.

are not permitted any longer. People has revealed against this and patches were proposed, but perl 5.16 still does not permit it. Some people say that this was a 'feature' of the parser not an intended behaviour (see comments in Reini's post).
In my case I switched to perl 5.14 and VCFtools was not working any more. At least I discovered it testing the test suit. 20 test failed all with the same error:

[..]
not ok 30 - Testing vcf-consensus .. perl -I../perl/ -MVcf ../perl/vcf-consensus  consensus.vcf.gz < consensus.fa
#   Failed test 'Testing vcf-consensus .. perl -I../perl/ -MVcf ../perl/vcf-consensus  consensus.vcf.gz < consensus.fa'
#   at test.t line 418.
#     Structures begin differing at:
#          $got->[0] = 'Use of qw(...) as parentheses is deprecated at ../perl//Vcf.pm line 1622.
#     '
#     $expected->[0] = '>1:1-500
[...]

I am lucky to be using perlbrew so I can change quickly from one version of perl to another (not so lucky that I need to reinstall a lot of CPAN modules.)