until (! -f "$md");

##</code><code>##

my $limit = 99999;
my $md;

# Creates unique tmpfile
do { 											#do the following 
	$tmpname = int(rand($limit));				#$tmpname = convert to integer random number between 0 and $limit (99999)
	$md      = "$TMPDIR/runitout_$tmpname";		#$md = "$TMPDIR/runitout_$tmpname" concatinated values of $TMPDIR (not listed) the string "/runitout_" and the value of $tmpname
} until (! -f "$md"); 							#until file $md does not exist