I realized I am checking for modified date twice. I have corrected my code.

 #!/usr/bin/perl
use strict;
use warnings;
use File::stat;
use Text::CSV_XS;
use IO::File;

 my $dirname = "Daily_QoS_CPD_link";
 opendir(DIR, $dirname) or die "Not able to open $dirname $!";
 
# Create an array of files in directory
 my @dir =  grep /\.csv/,  $dirname ne '.' && $dirname ne '..', readdi
+r DIR;
           rewinddir(DIR);
          
           
# create a list of csv's for today into a text file.
 my $One_day = 86400;
 foreach my $list (@dir){         
 my $diff = time()-stat("$dirname/$list")->mtime;
          if( $One_day > $diff){  
               open FILE, ">>CPD_Files.txt" or die "Not able to open f
+ile $!";
                     print FILE  "$list\n";
          }
}       
 closedir DIR;
 close FILE;
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