You might want to try and set the output pipe filehandle to non-blocking on linux. 
 
use Fcntl;
# set non blocking and unbuffered  
my $flags = fcntl( OUTHANDLE, F_GETFL, 0 );  
cntl( OUTHANDLE, F_SETFL, $flags | O_NONBLOCK ); 

select((select(OUTHANDLE), $|=1)[0]);

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In reply to Re: open3 buffering in linux vs. os x by zentara
in thread open3 buffering in linux vs. os x by Lexicon

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