but this program takes 5 minutes to respond

The problem probably is that the device isn't sending a newline, so the <$sock> (i.e. readline) keeps waiting for it until the socket is finally closed — which is likely what is happening due to a timeout after those 5 minutes...

Try sysread instead (with a length value larger than the response you expect). 

while ( sysread $sock, $_, 1000 ) {
        print $_;
}

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In reply to Re^3: IO::Socket Listen by Eliya
in thread IO::Socket Listen by Secalles

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