I think it has something to do with scoping rules:

$ perl -w -Mstrict
use Storable 'freeze';
my $c = freeze \4;
print "$c\n";
__END__
12�4

$ perl -w -Mstrict
eval "use Storable 'freeze'";
my $c = freeze \4;
Backslash found where operator expected at - line 2, near "freeze \"
        (Do you need to predeclare freeze?)
print "$c\n";
__END__
syntax error at - line 2, near "freeze \"
Execution of - aborted due to compilation errors.
[download]