use v5.14;
use warnings;

say "INPUT: ",my $str = join " ", 0 ..34;
my %DONT;
@DONT{1, 15, 16, 31}=();

my $stop=15;

my $donts = join "|", keys %DONT;
say my $dont_re = "(?!(?:$donts)\\b)";

  
while ( $str =~ m/\b$dont_re(\d+) \b$dont_re(\d+)/g ) {
  say "$1 $2";
  die unless $stop--;
  exists $DONT{$_} and die "$_ forbidden" for $1,$2;
}