thanks, that also works... so my choices are

my %webobj = (       
                'template' => param('template') || '', 
                'minscale' => param('minscale') || ''
            );
[download]

or

my %webobj = (       
                'template' => scalar(param('template')), 
                'minscale' => scalar(param('minscale'))
            );
[download]

From Randal's comment it seems the latter would be the wiser choice.

I am assuming 'minscale' is being assigned as a value to the 'template' key because there is nothing in param('template') and the comma is causing minscale to appear as part of a list.