The TRL-2 definition of the Rexx language defines the following built-in functions.
Hint: you can use the Tab key to sequence through the links.
Abbrev
Abs
Address
Arg
Bitand
Bitor
Bitxor
B2X
Center
Charin
Charout
Chars
C2D
C2X
Compare
Condition
Copies
Datatype
Date
Delstr
Delword
Digits
D2C
D2X
Errortext
Form
Format
Fuzz
Insert
Lastpos
Left
Linein
Lineout
Lines
Max
Min
Overlay
Pos
Queued
Random
Reverse
Right
Sign
Sourceline
Space
Stream
Strip
Substr
Subword
Symbol
Time
Trace
Translate
Trunc
Value
Verify
Word
Wordindex
Wordlength
Wordpos
Words
Xrange
X2B
X2C
X2D