It's not entirely clear to me quite what you want. However, here's an SSCCE showing one way to avoid processing the undef values.

use strict;
use warnings;
use feature 'say';

use Test::More tests => 2;
use Test::NoWarnings;

my %foo = (
    a => 1,
    b => 0,
    c => '',
    d => undef
);
my $lined = '';

foreach my $opt (sort keys %foo) {
    unless (defined $opt && defined $foo{$opt}) {
        no warnings 'uninitialized';
        say '9809 ', join '|', $opt, $foo{$opt};
        next;
    }

    # Only run these if $foo{$opt} is defined;
    $foo{$opt} =~ s/[^[:ascii:]]//gxms;
    $lined .= join ("\t", $opt, $foo{$opt})."\n";
}

is $lined, "a\t1\nb\t0\nc\t\n";

[download]

Note that your indentation is rather misleading and you haven't closed the outer loop. I've removed that outer loop here for simplicity.

In reply to Re: defined and value is 0 by hippo
in thread defined and value is 0 by redtux

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