$ perl -e '@a = (1 2 3 4); $y = join ",", @a'
Number found where operator expected at -e line 1, near "1 2"
	(Missing operator before  2?)
Number found where operator expected at -e line 1, near "2 3"
	(Missing operator before  3?)
Number found where operator expected at -e line 1, near "3 4"
	(Missing operator before  4?)
syntax error at -e line 1, near "1 2"
Execution of -e aborted due to compilation errors.

##</code><code>##

@a = (qw{1 2 3 4})