Is this the output you are looking for?

sample1STARsample2STARsample3*sample4*sample5
[download]

Here is what I used to generate this:

#!/usr/bin/env perl
 
use warnings;
use strict;
my $value = 'sample1\*sample2\*sample3*sample4*sample5';
$value =~ s#\\\*#STAR#g;
print "$value\n";
[download]

Note the escaped backslash in the regexp.