Your program ends with printing the prompt line. You nead to read a response from the user and then do what you wish with the result.

$|=1;
print "Choose a date and enter it on the command line: ";
my $user_response;
until ($user_response = <STDIN>){};
# do something with $user_response
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After Compline,
Zaxo

Update: improved it with autoflush, until and diamond