my @known_params = qw(foo bar baz); # of these you know

# this is a mockup of the passedParameters hash
my %passedParameters = (
    foo => 'oil',
    bar => 'lantern',
    baz => 'match',
    quux => 'half pig',
);

my %v = validateParams(%passedParameters);
print "valid parameters are:\n";
print "$_ => $v{$_}\n" for keys %v;

sub validateParams {
    my %args = @_;
    my %valid;
    for my $key (@known_params) {
        $valid{$key} = delete $args{$key}; # remove from input
    }
    if (keys %args) { # any keys left which we don't know?
        for my $key (keys %args) {
            warn "unknown parameter '$key' passed, value = '$args{$key}'\n";
        }
    }
    return %valid;
}
__END__
unknown parameter 'quux' passed, value = 'half pig'
valid parameters are:
baz => match
foo => oil
bar => lantern