package SelfLoader;
...
my %Cache;      # private cache for all SelfLoader's client packages
...

AUTOLOAD {
    our $AUTOLOAD;
    # $AUTOLOAD is fully-qualified function name, e.g. MyPackage::fn
    ...
    # set $Cache{$AUTOLOAD} to file text from __DATA__ to __END__
    ...
    delete $Cache{$AUTOLOAD};
    goto &$AUTOLOAD;
}