This was fixed in perl 5.8.8:

$ perl587 -wle 'print for qw(X Y) x 2'
Unquoted string "x" may clash with future reserved word at -e line 1.
Number found where operator expected at -e line 1, near "x 2"
        (Do you need to predeclare x?)
syntax error at -e line 1, near "qw(X Y) x "
Execution of -e aborted due to compilation errors.

$ perl588 -wle 'print for qw(X Y) x 2'
X
Y
X
Y
$
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Dave.