# as a for loop
for (@data} {
	$_ = '?'.$_	if $maxreject[$i]   && $_ > $maxclip 
			or $minreject[$i++] && $_ < $minclip
};
# or as a map, but different.
@data = map{ 
	   $maxreject[$i]   && $_ > $maxclip 
	or $minreject[$i++] && $_ < $minclip
	? '?'.$_
	: $_
} @data;