Here's one way:
my $message = sprintf('%d %s been loaded', $v, $v == 1 ? 'volume h
+as' : 'volumes have')
Here's a demonstration:
C:\>perl -E "say sprintf('%d %s been loaded', $_, $_ == 1 ? 'volume ha
+s' : 'volumes have') for 0 .. 9"
0 volumes have been loaded
1 volume has been loaded
2 volumes have been loaded
3 volumes have been loaded
4 volumes have been loaded
5 volumes have been loaded
6 volumes have been loaded
7 volumes have been loaded
8 volumes have been loaded
9 volumes have been loaded
C:\>
Alternatively (simpler):
my $message = sprintf 'Volumes loaded: %d', $v;