Good call. I inserted the "or die 'Can't open...$!'" command after the open command to get feedback on the error. Now running the code produces the error message: "Can't use string ("1000694-R201203014-C20111231-F10-"...) as a symbol ref while "strict refs" in use at Six_gramsC.pl line 20. That long numeric string is one of the file names I"m running through the batch (and representative of the other file names). Is there something inherently wrong with this filename, or is the program reading the file name where I'm trying to get it to read the file contents?

    open($fh, $file|) ;
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That generates a syntax error for me. Is that your exact code?

No--it looks like I must have added the | immediately prior to the initial posting. I've taken out the $fh from the code, so it now reads:

my @files = <*.htm>;
foreach $file (@files) {
    open($file or die "can not open .txt file: $!") ;
    while(<$file>) {
    my $dom = Mojo::DOM->new(<$file>);    
    my $text = $dom->all_text();
        for (split/\s+/, $text) {
            push @sequence, $_ ;
            if (@sequence >=10) {
            shift @sequence until @sequence ==10 ;
            ++$sequences{"@sequence"};
            }
        }
    }
}
close($file) ;
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This specification is what generates the "Can't use string..." error I cited.