Typically, I'll revert to a dispatch table for this sort of task:
my %dispatch = (
test => sub { print "test\n" },
hello => sub { print "hello\n" },
);
my $name = 'test';
$dispatch{$name}->();
$name = 'hello';
$dispatch{$name}->();
This has the benefit of confining your subroutines to a very small namespace, as opposed to the entire symbol table. You can validate your input (lookup the key before calling it), and thereby provide better diagnostics.
In the event I actually want the symbol table (I can't actually recall wanting this, outside of calling methods...) then I tend to prefer can(). It does have caveats: if you're dealing with a class, it will search up the inheritance tree. However, this is usually something I want.
my $name = 'test';
__PACKAGE__->can("update_$name")->();
$name = 'hello';
__PACKAGE__->can("update_$name")->();
sub update_test { print "test\n" }
sub update_hello { print "hello\n" }
You can similarly check for the function before simply calling it, by checking the return value of
can(), which is a subref.