You said:

I need to extract the data starting with "msg=" and ending just before "Src".

If that's really all you need to do, then a regex like this would extract just that portion:

while (<INPUT>) {
    my ( $msg ) = ( /msg=(.*?) Src \d+ / );
    # do something with $msg...
}
[download]

If you need other portions of the log entry as well, there are many ways to approach the task... Something like this should be easy to maintain:

while (<INPUT>) {
    next unless ( s/^([\d-]+)\s+([\d:]+)\s+(\S+)\s+// );
    chomp;
    my ( $date, $time, $ws2k ) = ( $1, $2, $3 );

    # remainder of log string contains an IP addess followed by
    # a set of "key=value string " tuples of various sizes

    my ( $ip, %flds ) = split /\s+(\w+)=/;  # parens keep key strings 
+in split output

    # do stuff with %flds and other vars...
}
[download]

Some of the hash values that end up in %flds may need further conditioning (e.g. removing quotes), but this while loop does a thorough parse of each log entry.

UPDATE: The latter while loop will do the wrong thing if it ever turns out that one of the log field values happens to contain a substring that matches "\w+=" (the split condition). If that's a valid risk, you could assign the result from split to an array, then build the hash from the array, based on your own prior knowledge about what the key strings are supposed to be (and what order they are supposed to be in).

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