use strict; 
use warnings;
use IO::File;

my @units = qw(foo bar);

foreach my $unit(@units){
    my $source = do{
        my $fh = IO::File->new;
        $fh->open("$unit.pm", "r") or die $!;
        read($fh, my $buffer, -s $fh);
        $fh->close;
        "package $unit;\n".$buffer;
    };
    eval "$source";
    $unit->foo();   # FQN: Der Name der Package ist das erste Argument!
}