my $text = ...;
...
my $pard = '\pard\plain\intbl\s0\ql\fi0\li0\ri0';

$text =~ s{
    \Q\cellx10464\E \Q$pard\E
    \Q\sl320\plain\f4\fs20\b\cf0 Patent Information\b0\E
    ([^\r\n]*[\r\n]){88} .* (EP\d{5,7})
    (([^\r\n]*[\r\n]){52}) .* \2 [\r\n]+
    ...
    \Q\cell\E \Q$pard\E \Q\plain\E
    }
    {tttttt$2 $4}xmsg;
...