check uri::escape...
update:

#!/usr/bin/perl -w
#-w courtesy of that nitpicker ! :)
use strict;
use URI::Escape;    

my $string = "valid / not valid \@ \$ ' ";
my $safe = uri_escape($string);
print $safe;
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Greetz
Beatnik
... Quidquid perl dictum sit, altum viditur.