I want to submit a form which has only one password field (Perl) and
the password should be submitted to a shell script.  In the shell
script, I want to process the pssword and use some crypting commands
to Encrypt it.

I do not know how I can process the password from Perl to shell and
how to obget it in Shell

Any help is appreciated. Thanks!

To call a shell script from perl, use the "system" statement in Perl.
Example follows.

Here is a perl script, tmp.pl
$password="test123";
system("tmp.sh $password");

Here is the called one-line shell script, tmp.sh:
echo "$1"

Here is how to run the perl script:
$ /usr/bin/perl tmp.pl

tmp.pl calls tmp.sh which outputs:
test123