Returns arg1 with all instances of arg2 replaced with arg3.
Example
{{#invoke:cmap|cmap|needle in haystack|needle|hay}}
local p = {} --p stands for package
function p.cmap(frame)
if frame.args[1] then
return mw.ustring.gsub(frame.args[1], '400px', '100px')[1]
end
return ''
end
return p