Precedence and operator binding is the issue. But...why not just.....

if (open FH, $log) {
....send tail of log file...
} else {
....send "server is down. Perl say $!"
}
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Note the error code (string reason) is set in $! if open, print, close, mkdir, unlink.....fail. Internal Perl functions return 1 if they succeed, 0 or undef if they fail. If you want to do the  || $scalar = 'blah' you can do this:

 
blah() || do{ $scalar = 'blah'; more_stuff() }
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