[Moo] setStyles({object})?

[keif]

I'm porting a function from prototype, and something the original
author does (that seems to break in MooTools) is do:
style = $extend({
        "float": a,
        marginTop: this.closeDimensions[s].height + 'px'
}
style["padding" + a.capitalize()] = this.border + 'px';
someEl.setStyle({style});

so MooTools chokes on using an object to set the styles - I *am*
converting setStyle to setStyles({style}), and broke it down to:

someEl.setStyles({
        'float': a,
        'margin-top': this.closeDimensions[s].height + 'px',
        'padding' + a.capitalize() = this.border + 'px'
});

and it throws an error on the third style saying it's missing a ':'
after the property ID.

Any ideas? TIA.