my @regexps = (
   qr{<ID>(.*?)</ID>},                      # ID
   qr{<TimeStamp>(.*?)</TimeStamp>},        # Time Stamp
   qr{<IP_Address>(.*?)</IP_Address>},      # IP Address
   qr{<Title>(.*?)</Title>},                # Title
   qr{<Complainant><Entity>(.*?)</Entity>}, # Reporting Entity
   qr{<Contact>(.*?)</Contact>},            # Reporting Entity Contact
   qr{<Address>(.*?)</Address>},            # Reporting Entity Address
   qr{</Phone><Email>(.*?)</Email>},        # Reporting Entity Email
);

my @xml_files = <*xml>;
for my $file (@xml_files) {
   for my $regexp (@regexps) {
      ...
      if ($line =~ $regexp) {
      ...
   }
}