Thank you for your help....I'm now in the process of looking at the tie module...My biggest problem is that each file is read into an array. I have to split each line of each array into yet another array, where I make a an update to one or two particular elements...That's where I get into trouble. I can't seem to make that change propagate back into the very first array (the one from which each line is made into a sub-array). Here's my code that I am working with. If you get overly bored, would you mind giving it a once-over? I am really at a loss here and have spent several days trying to make it work... Thanks again, Travis.

#!C:/Perl/bin/perl -w 
#use CGI ':standard';

open (UPDATE, "update.txt") or die "Cannot open update.txt";
@data = <UPDATE>;
close (UPDATE);
#SAMPLE DATA FROM THIS ARRAY IS AS FOLLOWS:
#T00001    0123-12345    DD001    67
#T00002    0123-12345    DD001    99
#T00003    0123-12345    DD002    0
#T00008    0123-12346    DD001    76
#T00014    7777-77777    DD001    88
#T00020    0999-99999    DD001    99

open (MDF, "mdfl.txt") or die "Cannot open update.txt";
@data2 = <MDF>;
@data2 = @data2;
close (MDF);

#SAMPLE DATA FROM THIS ARRAY IS AS FOLLOWS:
#T00001    0123-12345    DD001    100    100
#T00002    0123-12345    DD001    100    100
#T00003    0123-12345    DD001    100    100
#T00004    0123-12345    DD001    100    100
#T00007    0123-12345    DD002    100    100
#T00008    0123-12346    DD001    100    100
#T00013    7777-77777    DD002    100    100
#T00014    7777-77777    DD002    100    100
#T00015    7777-77777    DD003    100    100
#T00016    8888-88888    DD001    100    100
#T00019    8888-88888    DD003    100    100
#T00020    9999-99999    DD004    100    100


#I start by reading each line fo the first array, called @data
#I split this line on tabs
        foreach $line (@data) {  
        chomp $line;         
        @array = split (/\t/, $line);  
            $dmpiid = $array[0];                
            $be = $array[1];
            $osuf = $array[2];
            $update = $array[3];
        

#Then I read each line from the second array, splitting it on tabs too
            foreach $line2 (@data2) 
        {
            chomp $line2;
            @array2 = split (/\t/, $line2);              
                $dmpiid2 = $array2[0];                
                $be2 = $array2[1];
                $osuf2 = $array2[2];
                $last = $array2[3];
                $curr = $array2[4];

#next I find where certain values are the same from each array

        if (($dmpiid) eq ($dmpiid2)) {

#when found, I update the appropriate values as indicated

        $last = $curr;
        $curr = $update;
        
#next, I push the following string back into the @data2 array

    $new = "$dmpiid2\t$be2\t$osuf2\t$last\t$curr\n";
        push (@data2, $new);

#next I jump out of  the inner loop because there's no need to keep ch
+ecking
    
    
    last;

#however, once I do that, I need to delete the previous instance of
#the data I just updated, otherwise the array will contain both old an
+d 
#new data...this is where I get stuck

                        } #end if
        } #end inner foreach

}# end outer foreach


#this is my test which prints my results.  unfortunately, the old data
+ is 

present allong with the new data.
foreach $item (@data2) {
print "$item\n";
}
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