In perl, how do I replace a set of characters with a different set of characters in a single pass?

Question

Given ...

Ax~B~xCx~xDx

... emit ...

A~-B-~C~-~D~

I want to replace the ~ characters with - and the x characters with ~.

I could write ...

s/~/-/g;s/x/~/g; 

... but that (looks like it) passes over the string twice.

Answer 1

Use "transliterate" for replacement based on characters. Try this:

tr/~x/\-~/;

Answer 2

Since you're dealing with single characters, tr/// is the obvious answer:

tr/~x/-~/;

However, you're going to need s/// to deal with longer sequences:

my %subs = ( '~' => '-', 'x' => '~' );
my $pat = join '|', map quotemeta, keys %subs;
s/($pat)/$subs{$1}/g;