conditional text formatting

[jonty]

I am trying to parse text and then reassemble it for display conditional 
on the content of the text and set formatting accordingly.

But I am getting stuck on how to do this in shoes
para doesn't accept a block more's the pity

(say -  para do
if ... span("text", :stroke=>blue)
else span ("other" ;stroke=>red)
end
end)

Anyone help?