I have no idea if this is related to your problem, but...

When I try any variation of your command from the csh shell in UNIX, the !$ symbol is expanded to the last argument of my previous shell command. This happens whether you use single or double quotes around the Perl code.

Example using Perl v. 5.005:

% cd /etc
% perl -e 'do (!$var)'
perl -e 'do (/etcvar)'
Search pattern not terminated at -e line 1
[download]

The exact error message depends on whatever the previous command was, of course.

buckaduck