The workarounds:

Explicitly preceed the argument with the (numerical) parameter name in the call to template, like this:

    {MyUrl|1=http://www.example.com/abstract.cfm?uri=aa-123456}}


**Another solution**: one can create a symbolic name for the parameter. Then the template may look something like this:

    See here: [{{{link}}} (link)]

And the call like this:

    {MyUrl|link=http://www.example.com/abstract.cfm?uri=aa-123456}}


**Combine the solutions** to accept both named and ordered parameters for when there is no '=' sign there. The template (notice the empty string after '|' as a default value so that only one parameter is used):

    See here: [{{{link|}}}{{{1|}}} (link)]

This can be used with the call using 'link' above and also like this:

    {MyUrl|http://www.example.com/no/equal/signs/}}

Note, that the "combined" approach is not recommended due to inconsistency in parameter usage, unless there are too many calls across the wiki to the template using the ordered parameters, making it impractical to change all calls to the named parameter approach.