Codegolf: Quine and Antiquine This challenge is similar to Can you Meta Quine?

A quine is a program that produces itself on STDOUT. This challenge is to produce a program A which when run produces a program B on STDOUT. Program B when run produces program A on STDOUT. Programs A and B must be written in (and run in) the same language. The linked question constrained A != B. That looked too easy. So for this question, we insist A and B are antiquines, using the following rules:


Programs A and B may not use any of the same characters, save for whitespace and statement separators, and punctuation characters.
Programs A and B must each contain at least one character that is neither whitespace nor a statement separator, nor a punctuation character.
For the purpose of rules 1 and 2, the term 'whitespace' excludes any symbol or sequence of symbols which itself is a statement, operator or symbol that is interpreted (as opposed to a separator). Therefore in the Whitespace language, there is no whitespace.
A statement separator is a syntactic element conventionally used within the language to separate statements. This would include the newline in python, or the semicolon in Java, perl or C.
A punctuation character is an ASCII character which is neither whitespace nor in the POSIX word character class (i.e. an underscore is not punctuation for this purpose) - i.e ispunct() would return true, and it's not _.
Program A when run must produce a program (Program B) on its STDOUT, which when run in turn produces Program A.
Programs A and B must be in the same programming language.
The programming language used must actually be a programming language. Unless you make a good case otherwise, I'll suggest it must be Turing complete.
At least one of A and B must execute at least one statement within the language.


This is code golf, so the shortest answer wins, the score being the length of program A in bytes (i.e. the length of program B is not relevant).
Pascal (731 characters)

Program A:

program s;{$h+}uses sysutils;const p='program s;{$h+}uses sysutils;const p=';a='a';aa=''';';aaa='a=''';aaaa='''';aaaaa='begin write(lowercase(p+aaaa+p+aa+aaa+a+aa+a+aaa+aaaa+aa+aa+a+a+aaa+aaa+aaaa+aa+a+a+a+aaa+aaaa+aaaa+aa+a+a+a+a+aaa+stringreplace(stringreplace(stringreplace(stringreplace(aaaaa,aaaa,aaaa+aaaa,[rfreplaceall]),''lower''+''c'',''tm''+''p'',[]),''up''+''c'',''lower''+''c'',[]),''tm''+''p'',''up''+''c'',[])+aa+aaaaa))end.';begin write(upcase(p+aaaa+p+aa+aaa+a+aa+a+aaa+aaaa+aa+aa+a+a+aaa+aaa+aaaa+aa+a+a+a+aaa+aaaa+aaaa+aa+a+a+a+a+aaa+stringreplace(stringreplace(stringreplace(stringreplace(aaaaa,aaaa,aaaa+aaaa,[rfreplaceall]),'lower'+'c','tm'+'p',[]),'up'+'c','lower'+'c',[]),'tm'+'p','up'+'c',[])+aa+aaaaa))end.


Outputs program B:

PROGRAM S;{$H+}USES SYSUTILS;CONST P='PROGRAM S;{$H+}USES SYSUTILS;CONST P=';A='A';AA=''';';AAA='A=''';AAAA='''';AAAAA='BEGIN WRITE(UPCASE(P+AAAA+P+AA+AAA+A+AA+A+AAA+AAAA+AA+AA+A+A+AAA+AAA+AAAA+AA+A+A+A+AAA+AAAA+AAAA+AA+A+A+A+A+AAA+STRINGREPLACE(STRINGREPLACE(STRINGREPLACE(STRINGREPLACE(AAAAA,AAAA,AAAA+AAAA,[RFREPLACEALL]),''LOWER''+''C'',''TM''+''P'',[]),''UP''+''C'',''LOWER''+''C'',[]),''TM''+''P'',''UP''+''C'',[])+AA+AAAAA))END.';BEGIN WRITE(LOWERCASE(P+AAAA+P+AA+AAA+A+AA+A+AAA+AAAA+AA+AA+A+A+AAA+AAA+AAAA+AA+A+A+A+AAA+AAAA+AAAA+AA+A+A+A+A+AAA+STRINGREPLACE(STRINGREPLACE(STRINGREPLACE(STRINGREPLACE(AAAAA,AAAA,AAAA+AAAA,[RFREPLACEALL]),'LOWER'+'C','TM'+'P',[]),'UP'+'C','LOWER'+'C',[]),'TM'+'P','UP'+'C',[])+AA+AAAAA))END.


Outputs program A.