Something like this should work (not tested!):

use strict;
use warnings;

open my $fh, "<", "employees" or die "Cannot Open: $!";
my @employees;

while (<$fh>) {
    chomp;
    if (/(.*):(1.*):(.*):(.*):(.*)/) {
        push @employees, [ $1, $2, $3, $4, $5 ];
    }
}

close $fh;

@employees = sort { $a->[2] cmp $b->[2] } @employees;
for (@employees) {
    print join( "\t", @$_[ 2, 3, 0, 4 ] ), "\n";
}
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Update: bug fixed