package MyFilter;
use Filter::Simple;

FILTER {
    while (m/sub \s+ (\w+) \s+ : \s+ method/xg) {
        my ($name, $offset) = ($1, pos);
        $offset += $BYTE_OFFSET_FROM_WHERE_FILTER_WAS_INVOKED;
        warn "ondemand subroutine $name at byte offset $offset\n"
    };
};