in reply to Re^2: Different context
in thread mod_perl give 404 not_found with content

Definitely server side, but hey, got some more information to help you debug:

$ GET -S +s/Brake_lines/ GET +ke_lines/ --> 200 OK <html> <head><title>handler</title></head> <body> Hello from ME.<br /> </body> </html> <!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN"> <html><head> <title>200 OK</title> </head><body> <h1>OK</h1> <p>The requested URL /s/ was not found on this server.</ +p> </body></html>

Note that the server returned a 200 status with two responses merged into one.