Consider another example :

open( my $FILEHANDLE, '<', 'myfile.txt' );
$a=<$FILEHANDLE>; 

#<> returns just one line

open( my $FILEHANDLE, '<', 'myfile.txt' );
@a=<$FILEHANDLE>; 

#<> returns the whole file contents

the diamond operator returns different values depending on the context.