Below is the code, any Help Please, Thank you very much 
 use warnings ;

use Data::Dumper;

my %results = ();

while ( <DATA> ) {

chomp ;

my @row = split /,/, $_ ;

print STDOUT "row values is:".$_."\n";

if ( (exists $results{ $row[0], $row1 })) {

if ( ( $row2 ) <

$results{ $row[0], $row1 }->{ 'ACTDATE' }

) {

$results{ $row[0],$row1 }->{ 'ACTDATE' } = $row2 ;

}

print STDOUT "inactdate--".$row3." \n";

print STDOUT "in memory inact--".$results{ $row[0] }->{ 'INACTDATE' }.
+"\n";

if ( ( defined $row3) && !( defined $results{ $row[0] }->{ 'INACTDATE'
+ } )

) {

$results{ $row[0] }->{ 'INACTDATE' } = undef ;

}

elsif ( !( defined $row3) && ( defined $results{ $row[0] }->{ 'INACTDA
+TE' } )

) {

$results{ $row[0] }->{ 'INACTDATE' } = undef ;

}

elsif( ( $row3 ) > ( $results{ $row[0], $row1 }->{ 'INACTDATE' } ) )

{

$results{ $row[0], $row1 }->{ 'INACTDATE' } = $row3;

}

} else {

# Create new entry in hash

$results{ $row[0],$row1 } = {

'A1' => $row[0],

'B1' => $row1,

'ACTDATE' => $row2,

'INACTDATE' => $row3,

}

}

}

foreach ( sort keys %results ) {

my $a1 = $results{ $_ }->{ 'A1' } ;

my $b1 = $results{ $_ }->{ 'B1' } ;

my $actDt = $results{ $_ }->{ 'ACTDATE' } ;

my $inactDt = $results{ $_ }->{ 'INACTDATE' };

print "$a1,$b1,$actDt,$inactDt\n" ;

}

__DATA__

7900724655,200906888,20180416,20180522

7900724655,200906889,20180724,20180728

7900724655,200906889,20180601,20180720

7900724655,200906888,20180730,20180830

7900724655,200906890,20180905,20180930

7900724655,200906890,20181005,20181030

7900724655,200906890,20181104,

7900724666,200906868,20180416,20180522

7900724666,200906869,20180601,20180720

7900724666,200906869,20180724,20180728

7900724666,200906868,20180730,20180830

7900724666,200906890,20180905,20180930

7900724666,200906890,20181005,20181030

7900724666,200906890,20181104,

[download]

-------I am getting error as uninitialized variable----------

row values is:7900724655,200906888,20180416,20180522
row values is:7900724655,200906889,20180724,20180728
row values is:7900724655,200906889,20180601,20180720
inactdate--20180720
Use of uninitialized value in concatenation (.) or string at web_New_A
+DDON.pl line 16, <DATA> line 3.
in memory inact--
row values is:7900724655,200906888,20180730,20180830
inactdate--20180830
Use of uninitialized value in concatenation (.) or string at web_New_A
+DDON.pl line 16, <DATA> line 4.
in memory inact--
row values is:7900724655,200906890,20180905,20180930
row values is:7900724655,200906890,20181005,20181030
inactdate--20181030

[download]

2018-08-02 Athanasius added code tags

In reply to Re^4: sorting and merging in perl by Sekhar Reddy
in thread sorting and merging in perl by Sekhar Reddy

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.