I agree with imp that there may likely be some strange data in that line.

Here's a subroutine you could use to look at the line in question:

#
#  decode_string:  display the ascii value of each character of a stri
+ng
#
#     In:  $1 ... the string the decode
#          $2 ... (optional) number of characters to show per line
#          $3 ... (optional) a flag:  nonzero = hilight non-printing c
+hars
#          $4 ... (optional) a flag:  0 = show hex, nonzero = show dec
+imal
#          $5 ... (optional) the symbol representing non-printing char
+s
#
# Result:  Displays the value of each ascii character in the string,
#          with a summary of the string length, including number of
#          printable and non-printable characters.
#
sub decode_string {
    my ($str, $nper, $b_hi, $b_dec, $nonasc) = @_;

    # Defaults
    $b_dec  ||= 0;
    $nper   ||= ($b_dec? 12: 16);
    $nonasc ||= '.';
    $b_hi   ||= 0;

    # Anonoymous subroutines
    my $pprintable = sub { ($_[0] < 32 || $_[0] > 126)? 0: 1 };

    my $pshow_asc = sub {
        my ($idx, $pchars, $width) = @_;
        return unless @$pchars;
        $idx and map { print " " x (3 + $width) } ($idx .. $nper-1);
        print "  [";
        map { printf "%s", $pprintable->(ord $_)? $_: $nonasc } @$pcha
+rs;
        print "]";
        @$pchars = ( );
    };

    # Variable initialization
    my ($pasc, $idx, $ntext, $nnontext) = ([ ], 0, 0, 0);
    my $hilight  = $b_hi? "\e[101m": "";

    # Display the string
    print "-" x 79;
    my $len = length($str);
    foreach my $i (0 .. $len-1) {
        ($i % $nper) or $pshow_asc->($i, $pasc, $b_dec);
        ($i % $nper) or printf "\n %7d|", $i;
        push @$pasc, my $char = substr($str, $i, 1);
        my $hlchar = "";
        if ($pprintable->(ord $char)) {
            ++$ntext;
        } else {
            ++$nnontext;
            $hlchar = $hilight;
        }
        printf $b_dec? " $hlchar%3d\e[m": " $hlchar%02x\e[m", ord $cha
+r;
    }

    # Summary
    $pshow_asc->($len % $nper, $pasc, $b_dec);
    print "\n\n String length = $len  ";
    print "($ntext printable, $nnontext non-printable)\n", "-" x 79, "
+\n";
}
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Try calling decode_string($string, 0, 1), where $string is the line you want to look at, and it should hilight (in red) any bytes in the line which are non-printable.

    Sleeping even 1 second will take 40 minutes to run through the 2400 items.

It's a good point.  But you could slow things less abruptly with something like:

select(undef, undef, undef, 0.05);
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