perl search replace doesn't work

I am trying to run a simple search and replace

my @buffer = split /\=/, `metaflac --show-tag=Artist \"$inFile\" 2>&1`;
      my $artist = substr $buffer[1], 0, length($buffer[1])-1;
      $artist = ~ s/\//-/;

for some reason the output of $artist is 18446744073709551615

As soon as i try and search and replace I no longer a string returned only a long number.

I always find i waste the most time on the simplest of thigns in perl