I'll assume you are not kidding. You see the loop in the short script that calls system? Well if you put the perl code of the csv2xls script in there what do you think will happen?

Although you could put all the code in that loop that is very bad programming form. The best way to do it is to wrap the csv2xls functionality into a sub and simply replace the system call with a call to the sub.

use strict;

my $dir = "C:/some/dir";
my @files = glob("$dir/*.csv");

for my $file (@files) {
    print "Processing $file .....";
    my $ret_val = convert( $file );
    print ret_val == 0 ? "OK\n" : "Not OK Err: $ret_val\n";
}
print "Done!\n";

sub convert {
    my $file_to_convert = shift;
    # csv2xls code goes here
    # return 0 if conversion works OK
    # return error message if conversion fails
}
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