use vars qw($frob @mung %seen);
This pragma will predeclare all the variables whose names are in the list, allowing you to use them under "use strict", and disabling any typo warnings for them.
Unlike pragmas that affect the $^H hints variable, the "use vars" and "use subs" declarations are not lexically scoped to the block they appear in: they affect the entire package in which they appear. It is not possible to rescind these declarations with "no vars" or "no subs".
Packages such as the AutoLoader and SelfLoader that delay loading of subroutines within packages can create problems with package lexicals defined using "my()". While the vars pragma cannot duplicate the effect of package lexicals (total transparency outside of the package), it can act as an acceptable substitute by pre-declaring global symbols, ensuring their availability to the later-loaded routines.
See ``Pragmatic Modules'' in perlmodlib.