Or force a scalar context on the interpolated subroutine calls:

sub foo {
  wantarray() ? 10 : 1;
}

print 'Scalar context: ';
print ''. foo();
print ', ';
print foo() . "\n";

print 'List context: ';
print "@{[foo()]}, ";
print "${\foo()}\n";

print 'Scalar context: ';
print "@{[scalar(foo())]}, ";
print "${\scalar(foo())}\n";
__END__
Produces:
Scalar context: 1, 1
List context: 10, 10
Scalar context: 1, 1
[download]

But, while this is possible, I can't imagine it being preferable to concatenation for producing a scalar context.