I'm not aware of any modules for this, but I never looked as perl makes it so easy to this yourself.

#! perl -slw
use strict;

sub b2n{ eval '0b'. $_[0] }
sub n2b{ sprintf '%b', $_[0] }


my( $bs1, $bs2 ) = ( '0100100100101', '1010101010100' );

print "$bs1 + $bs2 = ", n2b( b2n( $bs1 ) + b2n( $bs2 ) );

__END__
P:\test>295453
0100100100101 + 1010101010100 = 1111001111001
[download]

If your bitstrings are longer than 32 bits (or 64 if your lucky enough to be using a 64-bit platform) then you might need something more elaborate.