The following makes no sense:

    if ($line =~ /Entering UPAuthModule::authenticate/ .. /Sending Inv
+alid credential/)
    {
        while ($line = <$log>)
        {
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You end up entering the if when you don't want to, then skipping a whole bunch of lines that have nothing to do with UPAuthModule with the inner while

Update: Even worse, the second m// in the above code matches against $_ instead of $line.

    if ($line =~ /Entering UPAuthModule::authenticate/
            ..
        /Sending Invalid credential/)
    {
        while ($line = <$log>)
        {
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