use strict;
use warnings;
use 5.010;
use List::MoreUtils qw(uniq);

my @data;

while (<DATA>) {
    my %row;
    @row{qw(employee form date)} = split /\s+/;
    push @data, \%row;
}

my @employees = uniq sort map { $_->{employee} } @data;

for my $employee (@employees) {
    say $employee;
    my @signed =
      sort { $a->[0] <=> $b->[0] }
      map  { [ $_->{form}, $_->{date} ] }
      grep { $_->{employee} == $employee } @data;
    for (@signed) {
        printf "\t%s\t%s\n", @$_;
    }
}

__DATA__
10001      10    20090101
10002      10    20080515
10003      10    20090323
10001      20    20090412
10002      20    20090711