use strict;
use warnings;

my $string = "non-printable or ill-behaved characters: \x0d \x0a \x00 \b \a";
# my $string = '';

print hexdump(\$string);


sub hexdump {
    my $str = ref $_[0] ? ${$_[0]} : $_[0];

    return "[ZERO-LENGTH STRING]\n" unless length $str;

    # split input up into 16-byte chunks:
    my @chunks = $str =~ /([\0-\377]{1,16})/g;
    # format and print:
    my @print;
    for (@chunks) {
        my $hex = unpack "H*", $_;
        tr/ -~/./c;                   # mask non-print chars
        $hex =~ s/(..)(?!$)/$1 /g;      # insert spaces in hex
        # make sure our hex output has the correct length
        $hex .= ' ' x ( length($hex) < 48 ? 48 - length($hex) : 0 );
        push @print, "$hex $_\n";
    }
    wantarray ? @print : join '', @print;
}


__END__

prints:

6e 6f 6e 2d 70 72 69 6e 74 61 62 6c 65 20 6f 72  non-printable or
20 69 6c 6c 2d 62 65 68 61 76 65 64 20 63 68 61   ill-behaved cha
72 61 63 74 65 72 73 3a 20 0d 20 0a 20 00 20 08  racters: . . . .
20 07                                             .