bash-2.03$ cat test.sh 
#!/bin/sh
echo "Enter Password:"
stty -echo
read PASSWD
stty echo
export PASSWD
test.pl

bash-2.03$ cat test.pl
#!/usr/local/bin/perl -w
my $passwd = shift || $ENV{'PASSWD'};
while(1) {
        print "blah balh\n";
        sleep 1;
}