You even have the logic to process the items from the getfiles subroutine already in place.

Maybe start with the following implementation for routine to see what happens:

sub routine {

    # identify filepath and name as parameters passed to routine
    my $file = shift;
    my $name = shift;
    print "routine called with '$file', '$name'\n";
}
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The next thing would be to give it a proper name. Find out what the routine should do, and then rename it to that.

Good names could be process_file or verify_md5 maybe. Or maybe the routine should do something different, but then its name should be different as well.

Thanks Corion... I think where I am struggling the most is how to process two files in tandem from the array... i.e. file and file.md5

What I am trying to achieve is to generate the MD5 of 'file' which already has been generated from an instrument prior to transfer and stored in a corresponding file called file.md5

Just how I get to work with these two files separately but concurrently from the rest of the array is what is failing me at the moment

Why do you want to process both, "file" and "file.md5"?

I think you want to do something different with "file" than you want to do with "file.md5".

Also note that if you know "file", you also know "file.md5", and if "file.md5" is not found that is an error.

You can blindly open "file.md5" without needing to verify its existence beforehand.

use warnings;
use strict;

use File::Slurp;

my @md5_file = read_file("md5");
my $md5_string = join( "", @md5_file );

my $dirname = "path/to/files/to/be/checked";
   while(my $file = (<'$dirname'/*>)) {
        
        open( my $fh, '<', $file );
        binmode($fh);

        my $md5 = Digest::MD5->new->addfile($fh)->hexdigest;

            if ( $md5_string =~ $md5) { 
                print "$md5 matches!\n";       
                } 
                else {        
                print "$md5 doesnt match ;(\n";
        }

}
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Even though it looks like this code works as is, I am not sure if does and I dont have the time to test it myself right now, but hopefully it will help you a little bit on your way :)

To save from creating a completely new thread, I am going to ask a question here, under the code I posted, and hope someone knowledgable reads it.

In the comparison operation 'if ( $md5_string =~ $md5 ){', would it be better to write it as 'if ( $md5 =~ $md5_string ){'

Think about it, what do the strings contain? Will "md2" =~ "md1\nmd2\nmd3\n" match?

use strict;
use warnings;
use Digest::MD5;

my $sourcedirectory = '//path/to/directory';

&main();

sub main {

    # creating file array
    my @files = &getfiles($sourcedirectory);
    # removal of the two directory structures which form the start of 
+the file array
    my $rmdir = shift (@files);
    my $rmdir2 = shift (@files);

    # capture of a count of the number of files remaining in the array
    my $filecount = @files;
    
    # check to see if there are no files, if none, exit script
    if ($filecount == 0) {
        print "\nNo files to process\n\n";
        exit;
    }
    # where there are files, the routine subroutine is called for each
+ item individually (except for md5 file types)
    else {
        foreach my $item (@files) {
            next if $item =~ /.md5/;
            my $filepath = "$sourcedirectory/$item";
            &routine($filepath, $item);
        }
    
    }
}


sub routine {

    # identify filepath and name as parameters passed to routine
    my $file = shift;
    my $name = shift;
    
    # open file, set to binary mode, close and process MD5
    open my $fh, '<', $file or die "Can't open file: $!";
    binmode ($fh);
    my $md5tocompare = &processmd5($fh);
    close $fh or die "Can't close file successfully: $!";
    
    # check file.md5 existence and open and read to memory
    open my $fh2, '<', "$file.md5" or next;
    my $originalmd5 = <$fh2>;
    close $fh2 or die "Can't close file successfully: $!";
    
    # check parity
    print "MD5 is $md5tocompare against orignal MD5 of $originalmd5\n"
+;
    
    next if $md5tocompare eq $originalmd5;
    &logmd5($md5tocompare, $name);
}

# subroutine to process the MD5 Hex value of a filehandle passed
sub processmd5 {
    
    my $io_handle = shift;
    my $md5 = Digest::MD5->new;
    $md5->addfile($io_handle);
    my $value = $md5->hexdigest;
    return $value;
    
}

# logreport subroutine that receives a string message as an argument, 
+and processes the log entry
sub logmd5 {
    
    # message, and definition of date/time variables to enable logging
    my $md5 = shift;
    my $md5filename = shift;
    my $md5file = "$sourcedirectory/Log.txt";
    # opening of log and appending of md5 to the log
    open(LOG, '>>', $md5file) or die "Can't open logfile $!";
    print LOG "ERROR: $md5filename does not match - $md5 is not the or
+iginal checksum";
    close LOG;

}

# a subroutine to enable definition of files to be processed
sub getfiles {
    
    my $sourcefiles = shift;
    my @file_list;
    opendir(DIR, $sourcefiles) or die "Can't open directory, $!\n";
    @file_list = readdir(DIR);
    closedir(DIR);
    return @file_list;
    
}
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I also have a script to generate the MD5 files if anyone needs it... just message me. Thanks!