while (<DATA>) {
	chomp;
	my ($userid, $password, $net_service_name) 
             = m#'?([^@/']+)?(/[^@/']+)?(@[^@/']+)?'?#;
	print "]]$_\[\[ 
  \tis parsed as \[$userid] \[$password] [$net_service_name]\n"
}   # while 

__DATA__
>>SYS/change_on_install@prod1<< <SYS> 
</change_on_install> <@prod1> 
>>rman/rman@rcat<< 
<rman> </rman> <@rcat> 
>>SYS<< <SYS> <> <> >>/<< <> </> <> 
>>/fooey<< <> </fooey> <> 
>>/fooey@foobar<< 
<> </fooey> <@foobar> 
>>SYS@foobar<< 
<SYS> <> <@foobar> 
>>'simple/fooey@foobar'<< 
<simple> </fooey> <@foobar>