$ cat tu.pl
while (<DATA>) {
    #$tmp = s/\*/\$lvl=/g; # LTS!
    $tmp = s{\*}{\$lvl=}g; # ?better?

    print "$_ : $tmp\n";
}
__DATA__
now is *the* time!
just how many asterisks? *****

$ perl tu.pl
now is $lvl=the$lvl= time!
 : 2
just how many asterisks? $lvl=$lvl=$lvl=$lvl=$lvl=
 : 5

 :