Util::prompt()

prompt( "label", $variable[, "description"])
The user is prompted to enter a variables value. The widget inhibits further program execution until the user pressed Exit or Cancel. $variable is used as a default. If the widget is terminated by Exit, the function returns the supplied value or undef, in case the user deleted the default value. If the widget is terminated by Cancel, it returns the default.
e.g.:
$pos = Util::prompt( "Pos", "1.234", "Select a target position");