What is your perl version?

If I run your program as:

my $n1 = '-933';
my $n2 = '-1039';

my $dif = $n1 - $n2;
print $dif . "\n";
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I get "106" as an output, which seems to be what you want.

Btw, here I have:

C:> perl -v
This is perl, v5.8.8 built for MSWin32-x86-multi-thread
(with 50 registered patches, see perl -V for more detail)

Binary build 820 [274739] provided by ActiveState
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