And, indeed, B::Deparse shows it to be so:

Win8 Strawberry 5.8.9.5 (32)  Thu 10/14/2021 17:49:15
C:\@Work\Perl\monks
>perl -Mstrict -Mwarnings -MO=Deparse,-p

my ($u, $v) = split /,/, 'U,V';
print "'$u' '$v' \n";

(my $w, my $x) = split /,/, 'W,X';
print "'$w' '$x' \n";

^Z
use warnings;
use strict 'refs';
(my($u, $v) = split(/,/, 'U,V', 3));
print("'${u}' '${v}' \n");
(my($w, $x) = split(/,/, 'W,X', 3));
print("'${w}' '${x}' \n");
- syntax OK

Win8 Strawberry 5.8.9.5 (32)  Thu 10/14/2021 18:54:22
C:\@Work\Perl\monks
>perl -Mstrict -Mwarnings

my ($u, $v) = split /,/, 'U,V';
print "'$u' '$v' \n";

(my $w, my $x) = split /,/, 'W,X';
print "'$w' '$x' \n";

^Z
'U' 'V'
'W' 'X'
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