~~Title: Arg~~
<evalcmd>
Arg && string && Value of the named argument. &&
argname && string && Name of the user command argument.
</evalcmd>

Returns the value of a [[:customize:the_customize_dialog:user_commands|user command]] argument. User commands can therefore use the Evaluator to modify their behavior
based on the value of a supplied argument.

//Example://
<code>
@if:=(Arg("NAME")=="jon")
echo Hi Jon!
@if:else
echo Who are you?
</code>