I'm on a fork challenged windoz box and can't run your program, and am also a bit pipe challenged myself. But since nobody replied yet I'll take a shot. My guess is you need to execute $shell_cmd using system and pipe it to CR: 

system ("$shell_cmd > &CR");

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In reply to Re: Tk and using a pipe to read command results by hangon
in thread Tk and using a pipe to read command results by drake50

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