PARSE defaults to breaking off tokens at blank spaces.

If you wish the value to be tokenized at characters other than a blank space, you can specify that as a literal string (we'll call the search string) after the token variable name. For example, assume that My_Variable's value is the string "This is some data; separated by a semi-colon, and then a comma". You wish to break this up into 3 tokens, separating the first token at the semi-colon (ie, "This is some data"), and the second token at the comma (ie, "separated by a semi-colon"), with the last token being "and then a comma".

Here's how we do that: 

/* Parse My_Variable into 3 tokens, broken at ; and , */
My_Variable = "This is some data;   separated by a semi-colon, and then a comma"
PARSE VAR My_Variable token.1 ';' token.2 ',' token.3
DO i=1 TO 3
   SAY "token."i "= '"token.i"'"
END
Note that since we aren't tokenizing by blank space, REXX doesn't trim the leading spaces off of the second token. You'd have to use the STRIP() function to subsequently do that.

You can token by entire strings (ie, patterns). For example, here we break apart the first token at the string "some", and the second token at the string "more". 

/* Parse My_Variable at the string "some" and "more" */
My_Variable = "This is some data; and this is more"
PARSE VAR My_Variable token.1 "some" token.2 "more" token.3
DO i=1 TO 3
   SAY "token."i "= '"token.i"'"
END
Note that the search strings "some" and "more" are completely removed from the tokens. If "some" did not appear in My_Variable at all, then the first token would contain the entire string, and the second and third tokens would be null strings. If "some" appeared, but "more" did not, then the first token would be "This is ", the second token would be the remaining data, and the third token would be a null string.

It's possible to tokenise the source data appearing inbetween search strings. For example: 

/* Parse My_Variable between "some" and "more" */
My_Variable = "This is some data; and this is more"
PARSE VAR My_Variable token.1 "some" token.1 token.2 token.3 "more"
DO i=1 TO 3
   SAY "token."i "= '"token.i"'"
END
The above tokenises everything between "some" and "more" and places the tokens in token.1 (ie, "data;"), token.2 (ie, "and"), and token.3 (ie, "this is ").

You can also use the value of a variable to contain the search string. You put the name of the variable in parentheses where you would otherwise put the search string: 

/* Parse My_Variable between "some" and "more" */
My_Variable = "This is some data; and this is more"
breakoff1 = "some"
breakoff2 = "more"
PARSE VAR My_Variable token.1 (breakoff1) token.1 token.2 token.3 (breakoff2)
DO i=1 TO 3
   SAY "token."i "= '"token.i"'"
END