use autodie qw( open close );

my $input_file  = 'clients.txt';
my $output_file = 'clients.csv';

open my $input_fh,  '<encoding(UTF-8)', $input_file;
open my $output_fh, '>encoding(UTF-8)', $output_file;

# Process the client data file...

close $input_fh;
close $output_fh;

exit 0;