As the subclasses that you're creating don't have any file scoped 'my' variables in them, you could create them with symbolic references instead of eval:

package WTF;

use strict;
use warnings;
use Carp;

sub define {
    my $self = shift;
    my $type = shift || croak "No type name";

    my ($parent, $subclass) =
        (__PACKAGE__, __PACKAGE__ . "\::$type");

    my $new = sub {
        my $self = shift;

        bless \( my $scalar ), $subclass;
    };
    {
        no strict 'refs';
        @{"${subclass}::ISA"} = ( $parent );
        *{"${subclass}::new"} = $new;
    }
    warn "Created type: $type\n";
}

sub import {
    my $self = shift;

    while (@_) {
        my ($nm, $list) = splice(@_, 0 ,2);

        __PACKAGE__->define($nm => $list);
    }
}

1;
[download]

then a small change to your script to dump out the symbol tables of the subclasses:

use strict;
use warnings;
use Data::Dump::Streamer;
use lib '.';

# Emulate use
BEGIN {
    require WTF;
    WTF->import(qw/some/);
    WTF->import(qw/more/);
}
Dump(\(%WTF::some::, %WTF::more::));
[download]

gives:

Created type: some
Created type: more
my ($subclass,$subclass_eclipse_1);
$subclass = 'WTF::some';
$subclass_eclipse_1 = 'WTF::more';
$HASH1 = {
           ISA => *WTF::some::ISA,
           new => *WTF::some::new
         };
*WTF::some::ISA = [ 'WTF' ];
*WTF::some::new = sub {
                    package WTF;
                    use warnings;
                    use strict 'refs';
                    my $self = shift @_;
                    bless \my($scalar), $subclass;
                  };
$HASH2 = {
           ISA => *WTF::more::ISA,
           new => *WTF::more::new
         };
*WTF::more::ISA = [ 'WTF' ];
*WTF::more::new = sub {
                    package WTF;
                    use warnings;
                    use strict 'refs';
                    my $self = shift @_;
                    bless \my($scalar), $subclass_eclipse_1;
                  };
[download]

You might also consider using Test::Class to manage the growing complexity of your test suite.