1. $sudo perl -MCPAN -e shell
2. cpan> install Unicode::Japanese
3. Save the following script (adapted largely from togdon's example) as full2half.sh and make it executable (chmod u+x):
   #!/bin/bash
   for file in *;do
   newfile=$(echo $file | perl -MUnicode::Japanese -e'print Unicode::Japanese->new(<>)->z2h->get;')
   test "$file" != "$newfile" && mv "$file" "$newfile"
   done
4. cd to desired directory and run script:
   $ /path/to/full2half.sh
   

1. Tools > Options... (in OS X it's OpenOffice.org > Preferences...)
2. Language Settings > Languages > check "Enabled for Asian languages" > OK
3. Highlight text > Format > Change Case > Full-width or Half-width

/nix | Jan 02, 2010