patchcmd – Change the def­i­ni­tion of an ex­ist­ing com­mand

The pack­age pro­vides a com­mand \patch­com­mand that can be used to add ma­te­rial at the be­gin­ning and/or the end of the re­place­ment text of an ex­ist­ing macro. It works for macros with any num­ber of nor­mal ar­gu­ments, in­clud­ing those that were de­fined with \De­clareRo­bustCom­mand.