This code:

for my $key (sort keys %client_total) {
 $client_total = {$key} = $client_total/10;
}
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does not make much sense to me. Perhaps you want something like this:

for my $key (sort keys %client_total) {
   $client_total{$key} = $client_total{$key}/10;
}
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Although, if this is what you want, there is no need to sort the keys for the calculation.

This could be done in a more concise (but less explicit) way:

$_/=10 for values %client_total;
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Or even possibly:

map {$_/=10} values %client_total;
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(Although I really prefer the previous solution.) Please also note that you posted this message twice and you got an answer from VincentK (look above), which might be what you are looking for.