Is this possible with regular expressions?

Question

Something like this:

/[abcd]/[efgh]/

The idea is that a will get replaced with e, b with f, c with g and so on.

Ideally, this should be language independent. If that isn't possible, I have an alternate solution (because this regex is generated by some code, I can make one for each of the possible replacements).

Answer 1

In perl, tr performs character replacement:

tr/abcd/efgh/

Will do what your example suggests.

Answer 2

In sed, the y/// expression does just that.

It's also a synonym for tr/// in perl