Okay, well, so in the general case (including '::' in module names), the non-string-eval way to do it seems to be:

# turn $class name into $path
my $class = 'Some::Class';
my $path  =  $class;
$path     =~ s/::/\//g;
$path    .=  '.pm';

# check if $path already loaded
if ( not exists $INC{$path} ) {

    # do block eval on $path
    eval { require $path };
    die "Can't load $class: $@" if $@;
}

# if we make it here, we can use $class
my $obj = $class->new;
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