Your data line is read into $_, but you are using $x for the match. To get separate the parts:

# $_ is the default buffer and pattern space
while(<DATA>){
    /^(\[\w+\])(.+)/;
    my $prefix = $1;
    my $values = $2;
    print "prefix:$prefix values:$values\n";
}
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Not sure if you require the square brackets in your result or not. Note that \w does not include a comma, and that there are, of course, many other ways to do it.