My first comment is that the way you are asking this question leaves a ton of room for interpretation.

If your "subroutne" is in a seperate .pl file how are you calling it? For sake of discussion I will assume you are doing something like:

#!/usr/bin/perl -w 
use CGI qw/ fatalsToBrowser/; # don't do this in production
use strict;
require "myfile.pl";

&foo(); # &foo is defined in myfile.pl
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In that case if I want to start my script over again with no regard to "state" or values of variables then within foo() I would simply

.
.
. #much handwaving

exec($0);
.
.
.
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Otherwise it gets slightly trickier. Check out the CGI.pm documentation and look at the redirect method. Yould do something like:

:
:
# NOTE: $q was defined elsewhere as my $q=new CGI;
print $q->redirect("http://my.site.tld/cgi-bin/foo.cgi?...")
:
:
:
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