diff --git a/sh.c b/sh.c
index 2d5565fc..1b73a600 100644
--- a/sh.c
+++ b/sh.c
@@ -112,34 +112,6 @@ static time_t  chktim;		/* Time mail last checked */
 char *progname;
 int tcsh;
 
-/*
- * This preserves the input state of the shell. It is used by
- * st_save and st_restore to manupulate shell state.
- */
-struct saved_state {
-    int		  insource;
-    int		  OLDSTD;
-    int		  SHIN;
-    int		  SHOUT;
-    int		  SHDIAG;
-    int		  intty;
-    struct whyle *whyles;
-    Char 	 *gointr;
-    Char 	 *arginp;
-    Char	 *evalp;
-    Char	**evalvec;
-    Char	 *alvecp;
-    Char	**alvec;
-    int		  onelflg;
-    int	  enterhist;
-    Char	**argv;
-    Char	**av;
-    Char	  HIST;
-    int	  cantell;
-    struct Bin	  B;
-    int		  justpr;
-};
-
 static	int		  srccat	(Char *, Char *);
 #ifndef WINNT_NATIVE
 static	int		  srcfile	(const char *, int, int, Char **);
@@ -152,10 +124,6 @@ static	void		  mailchk	(void);
 static	Char	 	**defaultpath	(void);
 #endif
 static	void		  record	(void);
-static	void		  st_save	(struct saved_state *, int, int,
-					 Char **, Char **);
-static	void		  st_restore	(void *);
-
 	int		  main		(int, char **);
 
 #ifndef LOCALEDIR
@@ -1569,7 +1537,7 @@ srcfile(const char *f, int onlyown, int flag, Char **av)
  * Save the shell state, and establish new argument vector, and new input
  * fd.
  */
-static void
+void
 st_save(struct saved_state *st, int unit, int hflg, Char **al, Char **av)
 {
     st->insource	= insource;
@@ -1659,19 +1627,28 @@ st_save(struct saved_state *st, int unit, int hflg, Char **al, Char **av)
     gointr	= 0;
     evalvec	= 0;
     evalp	= 0;
-    alvec	= al;
     alvecp	= 0;
     enterhist	= hflg;
     if (enterhist)
 	HIST	= '\0';
-    insource	= 1;
+    if (al == &fdecl) {
+	alvec	= NULL;
+	insource = 2;
+	st->fpipe = fpipe;
+	st->fdecl = *al;
+	flvl++;
+    }
+    else {
+	alvec	= al;
+	insource = 1;
+    }
 }
 
 
 /*
  * Restore the shell to a saved state
  */
-static void
+void
 st_restore(void *xst)
 {
     struct saved_state *st;
@@ -1696,6 +1673,12 @@ st_restore(void *xst)
 
     xclose(SHIN);
 
+    if (insource == 2) {
+	xclose(fpipe);
+	fpipe = st->fpipe;
+	fdecl = st->fdecl;
+	flvl--;
+    }
     insource	= st->insource;
     SHIN	= st->SHIN;
     if (st->OLDSTD != -1)
diff --git a/sh.decls.h b/sh.decls.h
index a863fede..5a18f99e 100644
--- a/sh.decls.h
+++ b/sh.decls.h
@@ -52,6 +52,8 @@ extern	void		  done		(int) __attribute__((__noreturn__));
 extern	void		  xexit		(int) __attribute__((__noreturn__));
 #endif
 extern	int		  grabpgrp	(int, pid_t);
+extern	void		  st_save	(struct saved_state *, int, int, Char **, Char **);
+extern	void		  st_restore	(void *);
 
 /*
  * sh.dir.c
@@ -150,6 +152,7 @@ extern	void		  doend		(Char **, struct command *);
 extern	void		  doeval	(Char **, struct command *);
 extern	void		  doexit	(Char **, struct command *);
 extern	void		  doforeach	(Char **, struct command *);
+extern	void		  dofunction	(Char **, struct command *);
 extern	void		  doglob	(Char **, struct command *);
 extern	void		  dogoto	(Char **, struct command *);
 extern	void		  doif		(Char **, struct command *);
@@ -164,6 +167,7 @@ extern	void		  dohup		(Char **, struct command *);
 extern	void		  doonintr	(Char **, struct command *);
 extern	void		  doprintenv	(Char **, struct command *);
 extern	void		  dorepeat	(Char **, struct command *);
+extern	void		  doreturn	(Char **, struct command *);
 extern	void		  dofiletest	(Char **, struct command *);
 extern	void		  dosetenv	(Char **, struct command *);
 extern	void		  dosuspend	(Char **, struct command *);
diff --git a/sh.err.c b/sh.err.c
index 9d9600ae..6b95f465 100644
--- a/sh.err.c
+++ b/sh.err.c
@@ -188,7 +188,11 @@ extern int enterhist;
 #define ERR_BADCOLORVAR	134
 #define ERR_EOF		135
 #define ERR_UNAVAILABLE	136
-#define NO_ERRORS	137
+#define ERR_UNDFUNC	137
+#define ERR_FUNCBEGIN	138
+#define ERR_FUNCALNUM	139
+#define ERR_RECURSION	140
+#define NO_ERRORS	141
 
 static const char *elst[NO_ERRORS] INIT_ZERO_STRUCT;
 
@@ -367,7 +371,10 @@ errinit(void)
     elst[ERR_BADCOLORVAR] = CSAVS(1, 137, "Unknown %s color variable '%c%c'");
     elst[ERR_EOF] = CSAVS(1, 138, "Unexpected end of file");
     elst[ERR_UNAVAILABLE] = CSAVS(1, 139, "%s: Feature is not available for this platform");
-
+    elst[ERR_UNDFUNC] = CSAVS(1, 140, "%S: Undeclared function");
+    elst[ERR_FUNCBEGIN] = CSAVS(1, 142, "Function name must begin with a letter");
+    elst[ERR_FUNCALNUM] = CSAVS(1, 143, "Function name must contain alphanumeric characters");
+    elst[ERR_RECURSION] = CSAVS(1, 144, "Too deep a recursion or nest");
 }
 
 /* Cleanup data. */
diff --git a/sh.func.c b/sh.func.c
index a9c0dd6f..a9862024 100644
--- a/sh.func.c
+++ b/sh.func.c
@@ -498,11 +498,18 @@ doexit(Char **v, struct command *c)
 	    stderror(ERR_NAME | ERR_EXPRESSION);
     }
     btoeof();
-#if 0
-    if (intty)
-#endif
-    /* Always close, why only on ttys? */
+
+    /* Always close, except in the context of
+     * dosource or dofunction.
+     * st_restore will handle. */
+    switch (insource) {
+    case 0:
 	xclose(SHIN);
+	SHIN = -1;
+	break;
+    case 2:
+	fdecl += Strlen(fdecl);
+    }
 }
 
 /*ARGSUSED*/
@@ -1096,6 +1103,11 @@ getword(struct Strbuf *wp)
 	stderror(ERR_NAME | ERR_NOTFOUND, "label");
 	break;
 
+    case TC_EXIT:
+	setname(short2str(Sgoal));
+	stderror(ERR_NAME | ERR_NOTFOUND, "return");
+	break;
+
     default:
 	break;
     }
@@ -2719,3 +2731,126 @@ getYN(const char *prompt)
 	continue;
     return doit;
 }
+
+int flvl,
+    fpipe = -1;
+Char *fdecl;
+
+void
+dofunction(Char **v, struct command *c)
+{
+    if (*++v == NULL) {
+	plist(&functions, VAR_READONLY);
+
+	return;
+    }
+    Sgoal = *v++;
+    Stype = TC_EXIT;
+    {
+	int pv[2];
+	struct saved_state st;
+	struct varent *varp;
+	Char *p;
+
+	if (!letter(*(p = Sgoal)))
+	    stderror(ERR_NAME | ERR_FUNCBEGIN);
+	while (*++p)
+	    if (!alnum(*p))
+		stderror(ERR_NAME | ERR_FUNCALNUM);
+	if ((varp = adrof1(Sgoal, &functions))) {
+	    if (flvl == 100)
+		stderror(ERR_RECURSION);
+	    mypipe(pv);
+	    cleanup_push(&st, st_restore);
+	    st_save(&st, pv[0], 0, &fdecl, v);
+	    fpipe = pv[1];
+	    fdecl = *varp->vec;
+	    process(0);
+	    cleanup_until(&st);
+
+	    return;
+	}
+	if (*v || c->t_dlef || c->t_drit ||
+	    c->t_dflg & (F_PIPEIN | F_PIPEOUT))
+	    stderror(ERR_UNDFUNC, Sgoal);
+	{
+	    Char funcexit[] = { 'r', 'e', 't', 'u', 'r', 'n', '\0' },
+		 alarg[] = { '!', '*', '\0' },
+		 *(*varvec)[4];
+	    struct Strbuf aword = Strbuf_INIT,
+			  func = Strbuf_INIT;
+	    struct wordent *histent = NULL,
+			   *ohistent = NULL;
+
+	    cleanup_push(&aword, Strbuf_cleanup);
+	    while (1) {
+		if (intty) {
+		    histent = xmalloc(sizeof(*histent));
+		    ohistent = xmalloc(sizeof(*histent));
+		    ohistent->word = STRNULL;
+		    ohistent->next = histent;
+		    histent->prev = ohistent;
+		}
+		if (intty && fseekp == feobp && aret == TCSH_F_SEEK)
+		    printprompt(1, bname);
+		(void) getword(&aword);
+		Strbuf_terminate(&aword);
+		if (intty && Strlen(aword.s) > 0) {
+		    histent->word = Strsave(aword.s);
+		    histent->next = xmalloc(sizeof(*histent));
+		    histent->next->prev = histent;
+		    histent = histent->next;
+		}
+
+		if (eq(aword.s, funcexit))
+		    break;
+		Strbuf_append(&func, aword.s);
+		Strbuf_append1(&func, ' ');
+		while (getword(&aword)) {
+		    Strbuf_terminate(&aword);
+		    if (intty && Strlen(aword.s) > 0) {
+			histent->word = Strsave(aword.s);
+			histent->next = xmalloc(sizeof(*histent));
+			histent->next->prev = histent;
+			histent = histent->next;
+		    }
+		    Strbuf_append(&func, aword.s);
+		    Strbuf_append1(&func, ' ');
+		}
+		func.s[func.len - 1] = '\n';
+
+		if (intty) {
+		    ohistent->prev = histgetword(histent);
+		    ohistent->prev->next = ohistent;
+		    savehist(ohistent, 0);
+		    freelex(ohistent);
+		    xfree(ohistent);
+		} else
+		    (void) getword(NULL);
+	    }
+
+	    if (intty) {
+		ohistent->prev = histgetword(histent);
+		ohistent->prev->next = ohistent;
+		savehist(ohistent, 0);
+		freelex(ohistent);
+		xfree(ohistent);
+	    }
+	    cleanup_until(&aword);
+	    if (!func.len)
+		return;
+	    Strbuf_terminate(&func);
+	    **(varvec = xcalloc(1, sizeof *varvec -
+				(sizeof **varvec * 2))) =
+	    func.s;
+	    setq(Sgoal, *varvec, &functions, VAR_READONLY);
+	    **(varvec = xcalloc(1, sizeof *varvec)) =
+	    Strsave(str2short(bname));
+	    (*varvec)[1] = Strsave(Sgoal);
+	    (*varvec)[2] = Strsave(alarg);
+	    setq(Sgoal, *varvec, &aliases, VAR_READWRITE);
+
+	    tw_cmd_free();
+	}
+    }
+}
diff --git a/sh.h b/sh.h
index 19bf10d6..721e5192 100644
--- a/sh.h
+++ b/sh.h
@@ -1019,7 +1019,9 @@ EXTERN struct varent {
 #define VAR_LAST        64
     struct varent *v_link[3];	/* The links, see below */
     int     v_bal;		/* Balance factor */
-}       shvhed IZERO_STRUCT, aliases IZERO_STRUCT;
+} shvhed IZERO_STRUCT,
+  aliases IZERO_STRUCT,
+  functions IZERO_STRUCT;
 
 #define v_left		v_link[0]
 #define v_right		v_link[1]
@@ -1266,6 +1268,36 @@ EXTERN nl_catd catd;
 extern int    filec;
 #endif /* FILEC */
 
+/*
+ * This preserves the input state of the shell. It is used by
+ * st_save and st_restore to manupulate shell state.
+ */
+struct saved_state {
+    int		  insource;
+    int		  OLDSTD;
+    int		  SHIN;
+    int		  SHOUT;
+    int		  SHDIAG;
+    int		  intty;
+    struct whyle *whyles;
+    Char 	 *gointr;
+    Char 	 *arginp;
+    Char	 *evalp;
+    Char	**evalvec;
+    Char	 *alvecp;
+    Char	**alvec;
+    int		  onelflg;
+    int	  enterhist;
+    Char	**argv;
+    Char	**av;
+    Char	  HIST;
+    int	  cantell;
+    struct Bin	  B;
+    int		  justpr;
+    int		fpipe;
+    Char	*fdecl;
+};
+
 #include "sh.decls.h"
 /*
  * Since on some machines characters are unsigned, and the signed
@@ -1305,5 +1337,10 @@ extern int    filec;
 #define TEXP_IGNORE 1	/* in ignore, it means to ignore value, just parse */
 #define TEXP_NOGLOB 2	/* in ignore, it means not to globone */
 
+extern int flvl, /* Level of nesting or recursion used
+		  * used by dofunction. */
+	   fpipe; /* Write end of a pipe used by dofunction. */
+extern Char *fdecl; /* Pointer to function declaration
+		     * used by dofunction. */
 
 #endif /* _h_sh */
diff --git a/sh.init.c b/sh.init.c
index 737afbc7..d751b754 100644
--- a/sh.init.c
+++ b/sh.init.c
@@ -80,6 +80,7 @@ const struct biltins bfunc[] = {
     { "fg",		dofg,		0,	INF	},
     { "filetest",	dofiletest,	2,	INF	},
     { "foreach",	doforeach,	3,	INF	},
+    { "function",	dofunction,	0,	INF	},
 #ifdef TCF
     { "getspath",	dogetspath,	0,	0	},
     { "getxvers",	dogetxvers,	0,	0	},
@@ -122,6 +123,7 @@ const struct biltins bfunc[] = {
     { "pushd",		dopushd,	0,	INF	},
     { "rehash",		dohash,		0,	3	},
     { "repeat",		dorepeat,	2,	INF	},
+    { "return",		dozip,		0,	0	},
 #ifdef apollo
     { "rootnode",	dorootnode,	1,	1	},
 #endif /* apollo */
diff --git a/sh.lex.c b/sh.lex.c
index 6651e55e..0c682dcc 100644
--- a/sh.lex.c
+++ b/sh.lex.c
@@ -1717,6 +1717,11 @@ bgetc(void)
 	    buf = (int) feobp / BUFSIZE;
 	    balloc(buf);
 	    roomleft = BUFSIZE - off;
+	    if (insource == 2) {
+		if (!*fdecl)
+		    return CHAR_ERR;
+		(void) xwrite(fpipe, fdecl++, (size_t) 1);
+	    }
 	    c = wide_read(SHIN, fbuf[buf] + off, roomleft, 0);
 	    if (c > 0)
 		feobp += c;
diff --git a/tcsh.man.in b/tcsh.man.in
index bde78ca3..fd8709f4 100644
--- a/tcsh.man.in
+++ b/tcsh.man.in
@@ -5424,12 +5424,14 @@ messages are verbose.
 .It Ic end
 .It Ic endif
 .It Ic endsw
+.It Ic return
 See the description of the
 .Ic foreach ,
 .Ic if ,
 .Ic switch ,
+.Ic while ,
 and
-.Ic while
+.Ic return
 statements below.
 .
 .El
@@ -5521,6 +5523,43 @@ the loop are executed.
 If you make a mistake typing in a
 loop at the terminal you can rub it out.
 .
+.It Ic function No (+)
+.It Ic function Ar name No (+)
+.It Ic \&...
+.It Ic return
+.It Ic function Ar name Xo
+.Op Ar arg No ...
+(+)
+.It Ar name Xo
+.Op Ar arg No ...
+(+)
+.Xc
+The first form of the command prints the value of all shell functions.
+.Pp
+The second form declares a function
+.Ar name Ns No .
+A declaration ends when a
+.Ic return
+is matched. (Both
+.Ic function
+and
+.Ic return
+must appear alone on separate lines.)
+May not be declared otherwise, and declared
+functions may not be redeclared or undeclared.
+.Pp
+The third form calls a function
+.Ar name Ns No ,
+optionally, preceded by
+.Ar arg Ns No ,
+which is a list of arguments to be passed.
+Function calls may be nested or recursive,
+but too deep a nest or recursion will raise an error.
+.Pp
+The fourth form is an
+.Ic alias
+for the third form.
+.
 .El
 .Bl -tag -width 6n
 .
@@ -10642,6 +10681,12 @@ and message catalog code to interface to Windows.
 .br
 Color ls additions.
 .
+.It Matheus Garcia ,
+2023.
+.br
+.Ic function
+built-in.
+.
 .El
 .
 .Sh THANKS TO
diff --git a/tests/commands.at b/tests/commands.at
index 48418cca..99049565 100644
--- a/tests/commands.at
+++ b/tests/commands.at
@@ -636,6 +636,39 @@ c
 AT_CLEANUP()
 
 
+AT_SETUP([function])
+AT_KEYWORDS([commands])
+
+AT_DATA([function.csh],
+[[
+if ( ! { function test test } ) then
+  echo 'FAIL: '\''function'\'' is not passing arguments!'
+  exit 1
+else if >& /dev/null ( { function test2 } ) then
+  echo 'FAIL: '\''function'\'' is not seeking for an ending exit!'
+  exit 1
+else if >& /dev/null ( ! { function test3 } ) then
+  echo 'FAIL: '\''function'\'' is not seeking for an ending exit on EOF!'
+  exit 1
+endif
+exit
+
+test:
+if ( "$1" == ) exit 1
+exit
+
+test2:
+exit
+echo test
+
+test3:
+exit
+]])
+AT_CHECK([tcsh -f function.csh])
+
+AT_CLEANUP()
+
+
 dnl
 dnl	getspath
 dnl
@@ -1870,3 +1903,22 @@ endif
 AT_CHECK([tcsh -f time_output.csh], 0, [ignore])
 
 AT_CLEANUP()
+
+AT_SETUP([main function])
+AT_KEYWORDS([commands])
+
+AT_DATA([main.csh],
+[[
+if >& /dev/null ( { function test } ) then
+  echo 'FAIL: '\''function'\'' is not seeking for an ending first exit!'
+  exit 1
+endif
+exit
+echo test
+
+test:
+exit
+]])
+AT_CHECK([tcsh -f main.csh])
+
+AT_CLEANUP()