my @words = (
   'foo',
   'bar',
);

foreach (@array) {
   foreach my $word (@words) {
      if (/\Q$word/) {  # BAD!! $word always changes.
         print;
         last;
      }
   }
}

##</code><code>##

my @words = (
   'foo',
   'bar',
);

foreach my $word (@words) {
   foreach (@array) {
      if (/\Q$word/) {  # GOOD!! regexp only recompiled when needed.
         print;
         last;
      }
   }
}

##</code><code>##

my @words = (
   'foo',
   'bar',
);

while (<FILE>) {
   foreach my $word (@words) {
      if (/\Q$word/) {  # BAD!! $word always changes.
         print;
         last;
      }
   }
}

##</code><code>##

my @words = (
   'foo',
   'bar',
);

# Precompile the regexps.
my @regexps = map { qr/\Q$_/ } @words;

while (<FILE>) {
   foreach my $regexp (@regexps) {
      if (/$regexps/) {     # GOOD!! $regexp is a compiled regexp.
     #if ($_ =~ $regexp) {  # GOOD!! Alternate syntax.
         print;
         last;
      }
   }
}

##</code><code>##

use Regexp::List ();

my @words = (
   'foo',
   'bar',
);

my $regexp = Regexp::List->new()->list2re(@words);

while (<FILE>) {
   print if /$regexp/;
  #print if $_ =~ $regexp;  # Alternate syntax.
}

##</code><code>##

my @patterns = qw(
   create
   drop
   delete
   update
   insert
);

my $regexp;
$regexp = Regexp::List->new(modifiers => 'i')->list2re(@patterns);
$regexp = qr/\b(?:$regexp)\b/;

...

while ($data = $sth->fetchrow_arrayref()) {
   # index is faster than regexps on constant strings.
   next if index(lc($data->[10]), 'tempdb') >= 0;

   if ($data->[13] =~ $regexp) {
      print "$data->[3] $data->[9] $data->[10] $data->[13]\n";
      last;
   }
}