my %h = (
	8   => 'value',
	3   => 'value',
	102 => 'value',
	4   => 'value',
	1   => 'value',
	57  => 'value',
);

my @keys = sort { $a <=> $b } keys %h;

my $try = shift || 5;	# this example allows user to specify on command line
my $low = 'not found';

foreach (@keys) {
	$low = $_ if $_ < $try;
	last if $_ >= $try;
}

print "$low\n";