There is no transliteration built into s///g. The OP's example was tr/abc/def/. s/// can't do that without some help (some kind of lookup structure, or embedding a tr command in the eval'd replacement, and in that case, why not just eval?).
Caution: Contents may have been coded under pressure.

In reply to Re^2: How to use a variable in tr/// by Roy Johnson
in thread How to use a variable in tr/// by perl-novice

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