$line = <$FILE>;
        until ( $line =~ /^c/ or $line =~ /^mt?\d+/ ) {
            ...
            $line = <$FILE>;
        }

##</code><code>##

while (<$FILE>) {
  if (m/^m/) { ... }
  elsif (m/^\s/) { ... }
  elsif (m/^c/) { ... }
  else { die "whoops - didn't expect: $_" }
}