Hi,

It's base 26 aritmetic :)

Base 10 aritmetic

The following adds 1 ten times to the number 0. The output is 10.

perl -e '$s=0;for $i (1..10) { ++$s }; print $s;'
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Base 26 aritmetic

The following adds '1' 26 times to the 'number' 'a'. The output is 'aa'.

perl -e '$s="a";for $i (1..26) { ++$s }; print $s;'
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