my $tableList = map qr/$_/i,
                join '|',
                map quotemeta,
                @tableList;

for my $Q (@fileList) {
   push @tableUsed, $Q =~ /$tableList/g;
}

##</code><code>##

my $tableList = map qr/$_/i,
                join '|',
                map quotemeta,
                @tableList;

my %tableUsed;
for my $Q (@fileList) {
   for my $W ($Q =~ /$tableList/g) {
      ++$tableUsed{$W};
   }
}

my @tableUsed = sort keys %tableUsed;