The thing that starts with "tethereal " is a string (not a "command"). I think your post is a little confusing, because the string contains "6 or 17", but you say you want to assign "6,7", to a variable called $protocol.

Anyway, the way to set up a regex to capture the pieces you want involves ignoring or escaping the regex-special characters (the parens in this case) -- something like this would do: 

$_ = "tethereal (proto 6 or 17) and src host suntest1 and dst host sun
+test2 -w /tmp/dumpfile";

( /\(proto ([^)]+)\) and src host (\S+) and dst host (\S+) -w (\S+)/ )
    and ( $protocol, $srchost, $dsthost, $dir ) = ($1,$2,$3,$4);

$protocol =~ s/ or /,/g;

[download]
(that is, if you want the value of $protocol to be a string consisting of comma-separated numbers, as opposed to something else)

Note the backslashes in front of the open and close parens that are intended to match actual parens in the string.

In reply to Re: How to escape parens for grep by graff
in thread How to escape parens for grep by swaroop

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