Close but no cigar

• What's wrong with this?

     use Timeout;

     sub halts {
       my ($source_code, $input) = @_;
       my $function = eval $source_code;

       # Run the function for at most an hour
       my $finished = with_timeout 3600, sub { $function->($input) };

       if ($finished) { return 1 }  # It finished within an hour
       else           { return 0 }  # It was still running after an hour
     }