If you use an array of hashes, the sorting becomes quite intuitive:

#! perl -slw
use strict;
use Data::Dump qw[ pp ];

my @data;
while( <DATA> ) {
    my( $col, $cnt, $stat, $miss, $mod ) = m[
        ^
        Collection=>(\d+) \s+
        ImageCount=>(\d+) \s+
        Status=>(\w+ ) \s+
        Missing=>( [1-9,]+ )? \s+
        Modified=>( .+ )
        $
    ]x or warn "Bad format at line $.\n" and next;

    my( $day, $mon, $year, $hrs, $min, $sec ) = 
        $mod =~ m[(\d+)/(\d+)/(\d+) (\d+):(\d+):(\d+)]
        or warn "Bad date format in line $." and next;

    push @data, {
        Collection => $col,
        ImageCount => $cnt,
        Status => $stat,
        Missing => [ split ',', $miss||'' ],
        Modified => sprintf( "%4d/%02d/%02d %02d:%02d:%02d",
            $year, $mon, $day, $hrs, $min, $sec ),
    };
}

##pp 'original order',  \@data;

## Sort data by image count descending and modified date ascending
my @ordered = sort {
    $data[ $b ]{ ImageCount } <=> $data[ $a ]{ ImageCount }
    ||
    $data[ $a ]{ Modified } cmp $data[ $b ]{ Modified }
} 0 .. $#data;

print  'Sorted by Image count descending and modified date ascending';
pp $data[ $_ ] for @ordered;

__DATA__
Collection=>168245 ImageCount=>6 Status=>SI Missing=>1,3 Modified=>01/
+18/2012 11:14:30
Collection=>161745 ImageCount=>6 Status=>I Missing=>2,3 Modified=>01/1
+8/2012 11:16:38
Collection=>162451 ImageCount=>6 Status=>SC Missing=> Modified=>01/20/
+2012 11:16:38
Collection=>117481 ImageCount=>8 Status=>C Missing=> Modified=>01/18/2
+011 7:16:38
[download]

Produces:

C:\test>junk53
Sorted by Image count descending and modified date ascending
{
  Collection => 117481,
  ImageCount => 8,
  Missing    => [],
  Modified   => "2011/18/01 07:16:38",
  Status     => "C",
}

{
  Collection => 168245,
  ImageCount => 6,
  Missing    => [1, 3],
  Modified   => "2012/18/01 11:14:30",
  Status     => "SI",
}

{
  Collection => 161745,
  ImageCount => 6,
  Missing    => [2, 3],
  Modified   => "2012/18/01 11:16:38",
  Status     => "I",
}

{
  Collection => 162451,
  ImageCount => 6,
  Missing    => [],
  Modified   => "2012/20/01 11:16:38",
  Status     => "SC",
}
[download]

Here's a quick stab at a solution. It works with your example data...

use strict;
use Data::Dumper;

my %hash;
my $regexp = qr{
    ^ \s*
        Collection \s* => \s* (\d+)? \s*
        ImageCount \s* => \s* (\d+)? \s*
        Status     \s* => \s* (\w+)? \s*
        Missing    \s* => \s* ([\d,]+)? \s*
        Modified   \s* => \s* ([\d/]+\s[\d:]+)? \s*
    $}x;

while (defined(my $line = <DATA>))
{
    chomp $line;
    my %linehash;
    if ($line =~ $regexp)
    {
        %linehash = ( 
            Collection   => $1,
            ImageCount   => $2,
            Status       => $3,
            Missing      => $4,
            Modified     => $5,
            );
    }
    next unless defined $linehash{Collection};
    $hash{ $linehash{Collection} } = \%linehash;
}

my @sorted_by_status = sort { $a->{Status} cmp $b->{Status} } values %
+hash;

print Dumper \@sorted_by_status;

__DATA__
Collection=>168245 ImageCount=>6 Status=>SI Missing=>1,3 Modified=>01/
+18/2012 11:14:30
Collection=>161745 ImageCount=>6 Status=>I Missing=>2,3 Modified=>01/1
+8/2012 11:16:38
Collection=>162451 ImageCount=>6 Status=>SC Missing=> Modified=>01/20/
+2012 11:16:38
Collection=>117481 ImageCount=>8 Status=>C Missing=> Modified=>01/18/2
+011 7:16:38
[download]

It would be nice if the regular expression could be made less specific, but some features of your data format make that tricky (e.g. the fact that the value following "=>" can be a zero-length string).

It would be nice if the regular expression could be made less specific, but some features of your data format make that tricky (e.g. the fact that the value following "=>" can be a zero-length string).

However, I think it's pretty much guaranteed that there will be whitespace between the key/value pairs. Yet, you use /\s*/. Also, nowhere do I see specified that there even may be whitespace around the "=>" — you just made that up. As this file looks to be computer generated, I sincerely doubt that this will ever be the case. Finally: the only place do I see whitespace inside a column value, is in the final column of the line: the timestamp.

In short: I think this regex will do:

/^Collection=>(\S*) \s+ 
  ImageCount=>(\S*) \s+
  Status=>(\S*) \s+
  Missing=>(\S*) \s+
  Modified=>(.*\S) /x
[download]

And if you do this:

my %r = 
    /^ (Collection)=>(\S*) \s+ 
       (ImageCount)=>(\S*) \s+
       (Status)=>(\S*) \s+
       (Missing)=>(\S*) \s+
       (Modified)=>(.*\S)
    /x;
[download]

you even get a nice hash record out of it, even though it is restricted to one match per line (otherwise, when using /g you'd get list context, with a different behavior as a result.

What would be the best way to extract all the information into a hash so that I can can perform sorts based on Collection, Status, and Modified?