$ perl -v | grep 'This is'
This is perl 5, version 16, subversion 3 (v5.16.3) built for x86_64-linux-thread-multi

$ perl -E'$_ = "abcde";             s/b../==${^MATCH}==/p;  say'
a====e

$ perl -E'$_ = "abcde"; $sub="b.."; s/$sub/==${^MATCH}==/p; say'
a==bcd==e