\long\def\prependef#1#2{\expandafter\def\expandafter#1\expandafter{#2#1}}
\long\def\appendef#1#2{\expandafter\def\expandafter#1\expandafter{#1#2}}
+% Variants of \def and \let, where the control sequence name is given as a string
+\def\sdef#1{\expandafter\def\csname#1\endcsname}
+\def\slet#1#2{\expandafter\let\csname#1\expandafter\endcsname\csname#2\endcsname}
+
\def\ucwwarn#1{\immediate\write16{*** Warning: #1 ***}}
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