use strict;     #### Always have these lines.  
use warnings;   #### They will save you lots of time debugging

use DBI;
use Time::localtime;
use File::Compare;

use XML::Simple; # qw(:strict);
use Data::Dumper;

my $user = "213256";

my @filesToProcess = glob "/export/home/$user/Tests/Match/dummy2*";    #### Need ""s.  ''s do not do variable interpolation

foreach my $file (@filesToProcess)
{
  open(FILE, $file) or die "Can't open `$file': $!";

  my $prev_var = -1_000_000;         #### set this to a value that will never appear as the numbers you need to check.
                                     #### (Obviously the 2-digit numbers must be in the range 0 to 99)

  while ( my $line = <FILE> )        #### do NOT read entire files into memory if they are big.  Much better to process them a line at a time
  {
    chomp $line;

    my $var = substr($line, 10, 2);  #### Do you mean substr($line,    9   , 2)?  substr() consders the first character to be at offset zero
        
    if ($var != $prev_var)           #### if number is different to number in previous line, then process it
    {
       $prev_var = $var;

       ... process $line here ....
    }
  }

  close FILE;
}

##</code><code>##

AB000000026JHAHKDFK
AB00000003033AFSFAS  = "30" line
AB000000028JHKHKHKJ
AB000000030HJHKH80J  = "30" line
AB0000000324446KJHK
AB000000030LOIKJUJ8  = "30" line