I hope nobody minds if I stick my nose in here.

I've been following the thread hoping that a perl wizard would post some cool code that I can stash in my toolbox.
The errors that Cleo reports look to me like they were generated by the shell, not by perl. When I try to execute the perl script I get a different error. I can come close to reproducing the error if I attempt to run the script as a bash shell script (which we would expect to fail):
ejl@dangpow:~$ bash test.pl
test.pl: undef: command not found
test.pl: line 4: syntax error near unexpected token `s/(/<'
test.pl: line 4: `s/(/<script language="JavaScript1\.2">.*?document\.captureEvents\(Event\.MOUSEUP\).*?document\.captureEvents\(Event.MOUSEDOWN\).*?<\/script>)//sm;'
###########
Here is the error I get running the perl script:
ejl@dangpow:~$ ./test.pl some.html
Unmatched ( before HERE mark in regex m/( << HERE / at ./test.pl line 4.
ejl@dangpow:~$ find . -name some.html -exec test.pl {} \;
Unmatched ( before HERE mark in regex m/( << HERE / at ./test.pl line 4.
###########
ejl@dangpow:~$ cat test.pl
#!/usr/bin/perl -pi
undef $/;
s/(/<script language="JavaScript1\.2">.*?document\.captureEvents\(Event\.MOUSEUP\).*?document\.captureEvents\(Event.MOUSEDOWN\).*?<\/script>)//sm;
###########
ejl@dangpow:~$ /usr/bin/perl -v
This is perl, v5.6.1 built for i686-linux
ejl@dangpow:~$ uname -a
Linux dangpow 2.4.26 #1 SMP Tue Apr 20 20:19:50 PDT 2004 i686 unknown