You said: another program will generate a big list of output similar to this :...

I'm wondering if this might be confusion about terminology. If you run that other program and it prints all this information on your screen, this is called the "standard out" (or "stdout") of that program. If you want your own perl script to read this in directly from that program (not from a disk file), then you simply place your perl script as part of a "pipeline" command, using the "vertical bar" character to join the output of that other command as the input to your perl script -- like this:

other_program arg1 arg2 | your_perl_script
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The vertical bar is the common shell syntax for creating pipeline commands in both MS-DOS Prompt and Unix command line interfaces. Mac OS X, being based on Unix, would also provide this syntax in a command line interface window.

This way your perl script simply needs to read STDIN, using the common idiom:

while (<>)
{
  # handle each line of data here
}
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(I'm sorry if I have misunderstood your question.)