A handler can receive values (called parameters) and use them as it runs.
You represent each value with a container called a parameter variable.
Parameter variables always follow the handler name in a comma-separated
list.
For example, when running the following mouseUp handler, HyperCard calls
sayMessage with two values, "red" and "apple". It then binds these values
to the parameter variables color and fruit in the sayMessage handler.
on mouseUp
sayMessage "red", "apple"
end mouseUp
on sayMessage color, fruit
put "I want a" && color && fruit
end sayMessage
You can use the variables color and fruit anywhere inside the handler. When
HyperCard sees them, it uses the values currently bound to them (the
variables remain bound only while the handler runs).
This article is adapted from the Claris Tech Info database.