Requires perl>=5.14.0 (/r)

use strict;
use warnings;

my $v = '/tmp/test';
while(<DATA>){
    s{`([^`\\]*(?>\\.|[^`\\]*)*)`}{$1 =~ s{(\$\w+)}{$1}eegr }eg;
    print;
}

__DATA__
test
--`cd \` $v`--
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