You don't need to use a substitution if you anchor the pattern using \G. And why not capture the odd elements as well?

my ( @even, @odd );
while ( $text =~ /\G ( [^,]+ ) (?: , ( [^,]+  ) )? (?: , | \z ) /gx ) 
+{
    push @even, $1;
    push @odd, $2 if defined $2;
}
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