Something like this? 
use strict;
use warnings;

chomp(my @title = split /\s+/, <DATA>);

my %emp;
while (<DATA>) {
    chomp(my @r = split/\s+/);
    push @{$emp{$r[0]}}, [ @r[1..$#r] ];
}

foreach (reverse sort keys %emp) {
    print "$_";
    foreach (@{$emp{$_}}) {
        print "\t$_->[0]\t$_->[1]\n";
    }
}

__DATA__
EmpNum  LOCATION  Shift
23        54        1
11        65        3
23        54        2

[download]
And the output -
23      54      1
        54      2
11      65      3

[download]

Updated: solution 2
use strict;
use warnings;
use Data::Dumper;

chomp(my @title = split /\s+/, <DATA>);
chomp(my @data = <DATA>);

my @sorted_data =
    map { $_->[1] }
    sort { $b->[0] <=> $a->[0] }
    map { [/^(\d+)/, $_] } @data;
    
my $last_emp = '';
foreach my $d (@sorted_data) {
    $d =~ s/^$last_emp\b/' ' x length($last_emp)/e;
    $d =~ /^(\d+)/ and $last_emp = $1;
    print "$d\n";
}


__DATA__
EmpNum  LOCATION  Shift
23        54        1
11        65        3
23        54        2

[download]

In reply to Re: complex input file by Roger
in thread complex input file by Anonymous Monk

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.