# ...
while (<DATA>) {
	my ($id, $string) = (split /[,\s]+/)[0,1];
	my $cur_len = length $string;
	next if defined $results{$id} and $cur_len > $results{$id}{len};
	$results{$id} = { str => $string, len => $cur_len };
}
say "$_ $results{$_}{str}" for sort keys %results;
#...