Your error is not in the use of qw// but in the use of for. The list over which for iterates must be in brackets. See:

$ perl -E 'for my $d qw( 2006-10-21 15.01.2007 10/31/2005 ) { say $d; 
+}'
syntax error at -e line 1, near "$d qw( 2006-10-21 15.01.2007 10/31/20
+05 )"
Execution of -e aborted due to compilation errors.
$ perl -E 'for my $d (qw( 2006-10-21 15.01.2007 10/31/2005 )) { say $d
+; }'
2006-10-21
15.01.2007
10/31/2005
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