Now to answer your question directly.

Adding guide comments simplifies the matter and makes it more reliable. 

function go
{
   if [ $1 = "--add" -o $1 = "--rem" ] ; then
      perl -e'
         use strict;
         use warnings;

         my ($key, $dir) = @ARGV;

         local $^I   = ".bak";
         local @ARGV = "$ENV{HOME}/.bashrc";
         while (<>) {
            my $f = /^\s*# -- BEGIN GO CASES --/
                    ..
                    /^\s*# -- END GO CASES --/;
            if (!$f || $f == 1) {
            }
            elsif ($f !~ /E/) {
               $_ = "" if /^\s*\(\Q$key\E\)/;
            }
            elsif ($dir) {
               my ($prefix) = /^(\s*)/;
               print("$prefix($key) cd $dir;;\n");
            }
         } continue {
            print
         }
      ' $2 $3
   else
      case $1 in
         # -- BEGIN GO CASES --
         (tmp)  cd $HOME/tmp;;
         (home) cd $HOME/home;;
         # -- END GO CASES --
      esac
   fi
}

[download]

Update: Switched to the desired syntax. 

go --add shortcut dir   (replaces if it already exists)
go --rem shortcut
go shortcut

[download]

I only tested the Perl components. The bash components were assumed to be correct.

Update: Fixed bug in if [ ... ].

In reply to Re: Appending in a switch case statement by ikegami
in thread Appending in a switch case statement by diffredential

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