You're on the right path with tr. 
$a = "A1";
$b = "B2";

printf("a: %s b: %s\n", $a, $b);

$a =~ tr/[12]/[21]/;
$b =~ tr/[12]/[21]/;

printf("a: %s b: %s\n", $a, $b);

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In reply to Re: replace a digit with another digit by cowboy
in thread replace a digit with another digit by kevyt

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