Strange, I don't have a proxy available but the string is formatted correctly:

perl -e @array1 = qw|localhost|; @array2 = qw|8080|; print `echo curl 
+-G -x $array1[0]:$array2[0] http://www.google.com`;
[download]

=== shows === curl -G -x localhost:8080 http://www.google.com