none any \p{..} could match it if donot set 'use utf8::all'.

This is exactly what \p{Lb=ZW} matches with no need for uft8::all:

use strict;
use warnings;

use Test::More tests => 5;

my $spacestr = "a\N{ZERO WIDTH SPACE}b";

isnt $spacestr, 'ab', 'String differs from plain "ab"';
is length ($spacestr), 3, 'Length is 3';
is substr ($spacestr, 1, 1), "\x{200B}", 'Middle char is U+200B';

like $spacestr, qr/\p{Lb=ZW}/, '\p{Lb=ZW} matches U+200B';

$spacestr =~ s/\p{Lb=ZW}//;
is $spacestr, 'ab', 'After stripping, string is plain "ab"';
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This is not to say that this is a good solution to phildeman's problem, of course. Far better just to get the decoding/encoding correct in the first place.