Help in deleting no right mouse click code from 10k of pages on server

[Cleo]

I'm getting this error

myscripts/remove-right-mouse-code.pl: undef: command not found
myscripts/remove-right-mouse-code.pl: line 5: syntax error near unexpected token `s/(/<'
myscripts/remove-right-mouse-code.pl: line 5: `s/(/<script language="JavaScript1\.2">.*?document\.captureEvents\(Event\.MOUSEUP\).*?document\.captureEvents\(Event.MOUSEDOWN\).*?<\/script>)//

I have my scripts in a non public directory so I can't do a link but here is a copy and paste from it.
#!/usr/bin/perl -pi

undef $/;
s/<script language="JavaScript1\.2">.*?document\.captureEvents\(Event\.MOUSEUP\).*?document\.captureEvents\(Event.MOUSEDOWN\).*?<\/script>//sm;