Run like

xsltproc --stringparam r2l no  blds2lttoolbox.xsl blds-lol-wat.xml > apertium-lol-wat.lol-wat.dix

xsltproc --stringparam r2l yes blds2lttoolbox.xsl blds-wat-lol.xml > apertium-lol-wat.lol-wat.dix

If the parameter r2l is yes, we flip the contents of <l> and <r>.