my @lines = ("foo*\n", "foo* \n", "foo*  \n");
for my $line (@lines) {
   $line =~ s/\*\s$//;
   print "($line)\n";
}
[download]

For the first input, the * and newline are removed. For the second input, the * and trailing space are removed, but the newline is left there. For the third input, nothing is removed. You might want to use this substitution instead:

   $line =~ s/\*\s*$//;
[download]