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;
      }
   }
}