use strict;
use warnings;

my $string = 'Hello,World,23,,,,
test,test,test
test,test,test
test,test,test
test,test,test
end,bye,,,,';

$string =~ s/((?:first line last word|last line last word),)[^\n]*/$1/g; #in your file

$string =~ s/((?:23|bye),)[^\n]*/$1/g; #here in this string


print $string;