my $string = q~*Elset, elset=KORN_10
232, 259, 260, 261, 286, 287, 288, 289, 290, 313, 314, 315
342, 343, 344, 345, 346, 347, 348, 371, 372, 373, 374, 375
..... und so weiter...
14556, 14557, 14558, 14581, 14582, 14583, 14584, 14585, 14609, 14610
*End Part~;

my $text = "Test\n";

$string =~ s/\*End Part/${text}*End Part/;
print $string;