our %RCache = (); keys( %RCache ) = 1020;

##</code><code>##

sub CheckMemoryUsage
{  our %RCache;
...

##</code><code>##

#! perl -slw
use strict;
use Devel::Size qw[ total_size ];

our %cache; keys %cache = 1020;
sub resetCache {
    our %cache;
    printf "Before: keys: %u size: %u\n",
        scalar keys %cache,
        total_size( \%cache );
    %cache = ();
    printf "After: keys: %u size: %u\n",
        scalar keys %cache,
        total_size( \%cache );
}

while( 1 ) {
    $cache{ int( rand 2**32 ) } = chr(0) x 2048;
    if( keys %cache >8192 ) {
        resetCache();
    }
}
__END__
C:\test>junk29
Before: keys: 8193 size: 17727631
After: keys: 0 size: 131144
Before: keys: 8193 size: 17727579
After: keys: 0 size: 131144
Before: keys: 8193 size: 17727590
After: keys: 0 size: 131144
Before: keys: 8193 size: 17727614
After: keys: 0 size: 131144
Before: keys: 8193 size: 17727556
After: keys: 0 size: 131144
Before: keys: 8193 size: 17727578
After: keys: 0 size: 131144
Before: keys: 8193 size: 17727621
After: keys: 0 size: 131144
...