The misspelling is right in the code I've posted, not in the module. In fact SVG.pm doesn't handle style specially in any way (though I've pondered it should).

I've now actually tested the code, and this seems to work (the resulting SVG displays fine in firefox and inkscape).

use v6;
use SVG;

my $r = 150 / 2;

my @parts = :circle[
    cx      => $r,
    cy      => $r,
    r       => $r,
    style   => 'fill:none; stroke: black; stroke-width: 1',
];

for 0, 2 ...^ 360 -> $degrees {
    my $rad = $degrees / 360 * 2 * pi;
    @parts.push: 'line' => [
        x1  => $r,
        y1  => $r,
        x2  => $r + $r * cos($rad),
        y2  => $r + $r * sin($rad),
        style   => 'stroke: black; stroke-width: 1',
    ];
}

say SVG.serialize:
    'svg' => [
        width  => 2 * $r,
        height => 2 * $r,
        @parts,
    ];
[download]

As for the xmlns:svg declaration, that just means that the svg XML namespace is set up as being interpreted as SVG. This allows you (in theory) to do fun stuff like embedding <svg:rect ...> elements straight into XHTML. But even for browsers that support it, it is only supported if the document is delivered as application/xml+xhtml, which is generally no fun, because most IE versions don't render such documents, but offer them for download. </rant>