do {
   $batch .= $line_B;
} until ( $line_B =~ m/^\s*go\s*$/i );

[download]

I suspect that your program would eventually die of memory exhaustion, assuming $line_B contains something.

Let's do a bit of detective work:

In reply to Re^5: readline() on unopened filehandle by fishbot_v2
in thread readline() on unopened filehandle by Win

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