always use the same perl in $PATH

always use the same perl in $PATH

Different tests may use unexpectedly different versions of perl,
depending on whether they hardcode the path to the perl executable or if
they resolve the path from the environment. This fixes it so that the
same perl is always used.

Fix some trailing whitespace and spelling mistakes as well.

CLA: trivial

Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Paul Dale <pauli@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/16362)