How could you find out size of a Hash in Perl?

%FM = ( 'Radio City' => 91.1,
              'Big FM' => 92.7,
              'Red FM' => 93.5,
              'Radio One' => 94.3,
              'Radio Mirchi' => 98.3,
              'Fever' => 104.0,
              'Oye FM' => 104.8,
              'FM Rainbow' => 107.1,
              'FM Gold' => 100.7);

print "size of Hash: ",scalar keys %FM,"\n";
# or
print "size of Hash:  " . keys ( %FM ) . ".\n";