If your using pack to do geometry management look at packPropagate I belive other managers have similar functions.

From Tk::pack
$master->packPropagate?(boolean)?
If boolean has a true boolean value such as 1 or on then propagation is enabled for $master, (see GEOMETRY PROPAGATION below). If boolean has a false boolean value then propagation is disabled for $master. In either of these cases an empty string is returned. If boolean is omitted then the method returns 0 or 1 to indicate whether propagation is currently enabled for $master. Propagation is enabled by default.

GEOMETRY PROPAGATION

The packer normally computes how large a master must be to just exactly meet the needs of its slaves, and it sets the requested width and height of the master to these dimensions. This causes geometry information to propagate up through a window hierarchy to a top-level window so that the entire sub-tree sizes itself to fit the needs of the leaf windows. However, the packPropagate method may be used to turn off propagation for one or more masters. If propagation is disabled then the packer will not set the requested width and height of the packer. This may be useful if, for example, you wish for a master window to have a fixed size that you specify.