Precedence problem there too; you need or instead of ||, or you need to parenthesize open's arguments. As is that's checking if $infilename is true (calling die if not), and then calling open and ignoring the return from it.

open( FH, MODE, FILE ) || die ERROR;
open FH, MODE, FILE or die ERROR;
[download]

Slight correction: the "<:utf8" asserts that the input file is UTF-8, and it is decoded as such. The preferred mode for this case these days is "<:encoding(utf-8)", which actually checks the encoding, failing if an invalid encoding is encountered. Yes, "<:utf8" appeared in older Perl documentation, which shows that better people than me failed to appreciate the distinction in the early going. It is mostly gone now.

Thanks, I've incorporated that. When I write the utf-8 as a file, do I also need to wrap it with that check?

######################################################################
+##################
sub write_file_utf8 {
    my $outfilename= shift; # appears in browser tabs
    my $outstr = shift; # file as a string
    ##################################################################
+##############
    open OUTFILE,  ">:utf8" , $outfilename 
        or die "cannot open >:utf8 $outfilename: $!";
    #binmode STDOUT, ":utf8";
    print OUTFILE $outstr, "\n";
    close(OUTFILE);
} #sub
[download]