Could you possibly forget to define a package gitadm_shell_commands in your gitadm_shell_commands.pm file?

Try checking symbol table for your sub in case it's left defined somewhere else:

{
 no strict 'subs';
 sub print_subs {
  for (keys %{$_[0]}) {
   next if $_ eq $_[0];
   print "$_[0]$_\n" if defined *{$_}{CODE};
   print_subs($_[0].$_) if /::$/; # dirty hack
  }
 }
 print_subs("main::");
}
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