use Sort::Maker;
print make_sorter(qw/plain string substr($_,10)/)->(<DATA>);

__DATA__
RRsnap02  2013-07-24 12:35:35
vmk000    2013-07-22 17:16:50
vmk001    2013-07-22 20:00:36
vmk009    2013-07-23 18:21:12
vmk010    2013-07-23 18:31:00
vmk020    2013-07-23 23:30:43
vmk024    2013-07-24 03:27:30
vmk031    2013-07-24 10:27:36
vmk032    2013-07-24 11:27:38
vmk032    2013-07-24 11:27:38

##</code><code>##

sort {
    do{
        my( $left, $right ) = map { substr($_,10) } $a, $b;
	$left cmp $right
    }
} @_;

##</code><code>##

return  map $_->[0],
	sort {$a->[1] cmp $b->[1]}
	map [ $_,
		do{ my ($val) = substr($_,10) ; $val }
	], @_  ;