Perl regular expressions can count as explained in perlretut - Perl regular expressions tutorial in the section on on matching repetitions. So /0{16}/ matches exactly 16 zeroes.

use strict;
use warnings;

my $line = "pvid 00c1be9a467335ce0000000000000000";
my $pvid;

if ($line =~ /pvid\s+(.*)0{16}$/) {
    $pvid = $1
}

print "$pvid\n";

__END__
00c1be9a467335ce
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Since the string you are trying to extract consists of hex digits, a slight improvement on the regex might be:  /pvid\s+([[:xdigit:]]*)0{16}$/ . Go to perldoc.perl.org and search for "character class" to learn more ...