fenixpar – One-shot changes to token registers such as \everypar

The bun­dle pro­vides two pack­ages, fenx­i­tok and fenix­par.
The fenix­tok pack­age pro­vides user macros to add ma­te­rial to a to­ken reg­is­ter; the ma­te­rial will be (au­to­mat­i­cally) re­moved from the to­ken reg­is­ter when the reg­is­ter is ex­e­cuted. Ma­te­rial may be added ei­ther to the left or to the right, and care is taken not to over­ride any re­def­i­ni­tion that may be in­cluded in the to­ken reg­is­ter it­self.
The fenix­par pack­age uses the macros of fenix­tok to pro­vide a user in­ter­face to ma­nip­u­la­tion of the \ev­ery­par to­ken reg­is­ter.
The pack­ages re­quire the e-TeX ex­ten­sions; with them, they work ei­ther with Plain TeX or with LaTeX.