regexp matching newline

hello

i have a problem removing blank lines in one regexp. my string will be 
slurped so it will contain newlines as examplified below:

my $str = qq(test0;
test1;
//test2;
test3;);

$str =~ s,^.*//.+;$,,igm;

print $str;

__END__



this is the result:
---------------------
test0;
test1;

test3;



i want t achieve:
----------------------
test0;
test1;
test3;