: make-string ( -- s )
    s" foo" ;

: append-print ( s s -- )
    append type cr ;

make-string s" bar" append-print

$ gforth prob1.fs -e bye
gforth(41572,0x7fff79cc2310) malloc: *** error for object 0x103a551a0: pointer being realloc'd was not allocated
*** set a breakpoint in malloc_error_break to debug

Abort trap: 6.

variable foo
s" foo" foo !

foo s" bar " append type cr

$ gforth prob2.fs
foo��^C
in file included from *OS command line*:-1
prob2.fs:4: User interrupt
foo s" bar " append >>>type<<< cr
Backtrace:
$10C7C2E90 write-file

see append
: append
  >l >l >l >l @local0 @local1 @local3 + dup >l resize throw >l @local4 @local0 @local3 + @local5
  move @local0 @local1 lp+!# 48 ; ok

: make-string ( -- s )
  s" foo" ;

: append-print
  s+ type cr ;

make-string s" bar" append-print

$ gforth b.fs -e bye
foobar

: append { addr1 u1 addr2 u2 -- addr u }
    addr1 u1 u2 + dup { u } resize throw { addr }
    addr2 addr u1 + u2 move
    addr u ;

: s+ { addr1 u1 addr2 u2 -- addr u }
    u1 u2 + allocate throw { addr }
    addr1 addr u1 move
    addr2 addr u1 + u2 move
    addr u1 u2 +
;

: astring S" foo" ;

  CREATE buffer 100 ALLOT  space for 100  chars

   Put the first string in `buffer and append the second string.

   Also print the second string

 : append-print ( s s -- )

 type cr 2swap

 buffer $!

 buffer $+! ;

 astring s" bar" append-print

  bar OK  answer

  buffer $@ TYPE

  foobar OK  answer