use strict;

my $length = 164;

my $file = 'path/to/filename.txt';

open(my $F, '<:encoding' , $file) 
or die "cant open $file\n$!\n"; 

# you will supply the right value for 'encoding'.  
# one common example is 'utf8'

while( read( $F, my $record, $length ) ){
    # do something with $record
}

##</code><code>##

my $c = 'some_scalar_data';

test_for_wide_chars: {
    
    require bytes;
    
    if ( bytes::length($c) > length($c) || 
           ($] >= 5.008 && $c =~ /[^\0-\xFF]/)) {   
         
        print "i found a wide character!"              

    }

    no bytes;

}