I went through the code, making changes mostly for practice. It is *untested*. Hopefully the comments are of use. Furthermore, hopefully others can criticize me for my deficiencies:

#use strict;

# don't disable strict. Period.

# you are only using $comparetime within the compare() function
# If you define it here, then it should be passed to the sub as
# a parameter

my $comparetime="0";

# sub compare; # no need for this

my $Clinrxdir="D:\\StoreAccess\\shared\\sup shared\\";

opendir(DIR,$Clinrxdir);
my @Files= readdir(DIR);
closedir(DIR);

for my $cpupdate (@Files){

    if($cpupdate =~ m/\s*cp_/i){

        my $m_time = (stat($Clinrxdir.$cpupdate))[9];

    # what does a print() say about $m_time here?

        my ($i_wday, $i_month, $day, $year) = (localtime($m_time))[6,4
+,3,5];
    
    # why are you breaking $m_time up. Depending on what you want to d
+o,
    # it may be easiest to simply compare $m_time as an int

        my $comparison = compare($orig_mtime, $cmp_mtime $cupupdate);

        print "Timestamp for " . $cpupdate . " " . $m_time ."\n";

    }
}

# I'm lost as to where $file comes from here...

print "This is a test of file = " . $file . "\n";
print $file;

system("pause");


sub compare(){
    my ( $orig_mtime, $cmp_mtime, $cpuupdate ) = @_;
    if($cmp_mtime > $orig_mtime){
        my $file = $cpupdate;
    }
    else{
        #else{$comparetime=$string;}
    
    # it looks like you are trying to cause more than one side
    # effect with your subroutine, as opposed to focusing on providing
    # a single return. Personally, I've learned that mixing function
    # programming with global data will lead to bugs that are very
    # difficult to track down.
    
    # if you want to set $comparetime to $string, you should do it 
    # outside of this routine, after you've collected up compare()
    # result
    }
}
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Steve

First, you have to remember that readdir returns every directory entry, including "." and ".." (which are directories, as you must know, and which could often, by coincidence, be dated more recently than any data file in the directory).

If you want to pick the most recent entry in a directory (not including "." or ".."), then try something like this:

#!/usr/bin/perl

use strict;
use File::Spec;

my $Usage = "Usage: $0 pathname\n";
die $Usage unless ( @ARGV == 1 and -d $ARGV[0] );

my $path = shift;
opendir( D, $path ) or die "$path: $!\n";

my %files;
for my $file ( grep !/^.{1,2}$/, readdir D ) {
    my $filepath = File::Spec->catfile( $path, $file );
    my $file_age = -M $filepath;
    $files{$file_age} = $file;
}

my @age_order;
push @age_order, $files{$_} for ( sort {$a<=>$b} keys %files );

print "Newest file in $path is: $age_order[0]\n";
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