use strict;
use warnings;

my @lines = (
'012345 NA13333 C C',
'012345 NA13334 F F',
'012345 NA13335 E F',
'012346 NA13333 U U',
'012346 NA13334 I I',
'012346 NA13335 Y O');

foreach my $line (@lines) {
    next unless $line =~ m{^(\S+) NA(\d+) (.*)};
    my ($site, $userID, $data) = ($1, $2, $3);
    print "SITE: $site   USER: $userID   DATA: $data\n";
}