• Extensive list management (csv lists, lists of single tokens/characters, etoolbox lists);
• purely expandable loops (csvloop, forcsvloop, etc.);
• conversion (csvtolist, etc.));
• addition/deletion (csvadd, listdel, etc.);
• Expansion and group control: \expandnext, \ExpandAfterCmds, \AfterGroup…;
• Tests on tokens, characters and control sequences (\iffirstchar, \ifiscs, \ifdefcount, \@ifchar…);
• Tests on strings (\ifstrnum, \ifuppercase, \DeclareStringFilter…);
• Purely expandable macros with options (\FE@testopt, \FE@ifstar) or modifiers (\FE@modifiers);
• Some purely expandable numerics (\interval, \locinterplin).

See also etoolbox.

The author is Florent Chervet. The package is Copyright © 2009 Florent Chervet.