No, it's not limited to just parens for delimiters. I get the same behaviour with other delimiters.

use warnings;
@array = qw!X! x 2;
print @array, "\n";
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gives

Unquoted string "x" may clash with future reserved word at 541179.pl l
+ine 2.
Number found where operator expected at 541179.pl line 2, near "x 2"
        (Do you need to predeclare x?)
syntax error at 541179.pl line 2, near "qw!X! x "
Execution of 541179.pl aborted due to compilation errors.
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