use strict;
my $str = '1281674 the crescent annandale 02/10/2019 16/10/2019 - 16/11/2019 pending 1281640 city west link rd lilyfield 02/10/2019 16/10/2019 - 16/11/2019 pending 1276160 victoria rd rozelle 25/09/2019 14/10/2019 - 15/10/2019 pending 1331626 31/12/2019 - 31/01/2020 incomplete n/a 1281674 the crescent annandale 02/10/2019 16/10/2019 - 16/11/2019';
my $regex = qr/\b\d{7}\b(?=(?:(?!\b\d{7}\b).)*incomplete n/a).*?$/mp;
my $subst = '';
my $result = $str =~ s/$regex/$subst/rg;
print "The result of the substitution is' $result\n";
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Perl, please visit: http://perldoc.perl.org/perlre.html