#!/usr/bin/perl -w
use strict;

my $cmd;
while ((print "enter cmd: "), $cmd=<STDIN> and $cmd !~/^\s*$/)
{
    chomp $cmd;
    print "cmd was: $cmd\n";
}
print "loop exited\n";

##</code><code>##

my $cmd="";
until ($cmd !~ /^\s*$/){print "enter cmd: "; $cmd=<STDIN>;}

chomp $cmd;
print "cmd was: $cmd\n";