This chapter replicates the REPL help system contents, also
found in the repository in
docs/help.txt.
It is the practical reference for the language.
More in-depth explanations of specific topics can be found
in the
FAQ
chapter.
TOPICS HELP Type help TOPIC or h TOPIC where TOPIC is one of: "s" syntax "t" value types "v" verbs (like +*-%,) "nv" named verbs (like in, sign) "a" adverbs (/\') "tm" time handling "rt" runtime system "io" IO verbs (like say, open, read) op where op is a builtin's name (like "+" or "in") Notations: i (integer) n (number) s (string) r (regexp) d (dict) t (dict S!Y) h (handle) e (error) f (function) F (dyadic function) x,y,z (any other) I,N,S,X,Y,A (arrays) SYNTAX HELP numbers 1 1.5 0b0110 1.7e-3 0xab 0n 0w 3h2m strings "text\x2c\u00FF\n" "\"" "\u65e5" "interpolated $var" qq/$var\n or ${var}/ qq#text# (delimiters :+-*%!&|=~,^#_?@`/) raw strings rq/anything until single slash/ rq#doubling ## escapes# arrays 1 2 -3 4 1 "ab" -2 "cd" (1 2;"a";3 "b";(4 2;"c");*) regexps rx/[a-z]/ (see https://pkg.go.dev/regexp/syntax for syntax) dyadic verbs : + - * % ! & | < > = ~ , ^ # _ $ ? @ . (right-associative) monadic verbs :: +: -: abs uc error ... adverbs / \ ' (alone or after expr. with no space) (left-associative) expressions 2*3+4 → 14 1+|2 3 4 → 5 4 3 +/'(1 2 3;4 5 6) → 6 15 separator ; or newline except when ignored after {[( and before )]} variables x y.z f data t1 π (. only allowed in globals) assign x:2 (local within lambda, global otherwise) x::2 (global) op assign x+:1 (sugar for x:x+1 or x::x+1) x-:2 (sugar for x:x-2) list assign (x;y;z):e (where 2<#e) (x;y):1 2;y → 2 eval. order apply:f[e1;e2] apply:e1 op e2 (e2 before) list:(e1;e2) seq: [e1;e2] lambda:{e1;e2} (e1 before) sequence [x:2;y:x+3;x*y] → 10 (bracket not following noun tightly) index/apply x[y] or x y is sugar for x@y; x[] ~ x[*] ~ x[!#x] ~ x (arrays) index deep x[y;z;...] → x.(y;z;...) (except for x in (?;and;or)) index assign x[y]:z → x:@[x;y;:;z] (or . for x[y;...]:z) index op assign x[y]op:z → x:@[x;y;op;z] (for symbol op) lambdas {x+y-z}[3;5;7] → 1 {[a;b;c]a+b-c}[3;5;7] → 1 {?[x>1;x*o x-1;1]}5 → 120 (o is recursive self-reference) projections +[2;] 3 → 5 (2+) 3 → 5 (partial application) compositions ~0> → {~0>x} -+ → {- x+y} *|: → {*|x} index at field x..a → x["a"] (.. binds identifiers tightly, interpolable) field expr. ..a+b → {x["a"]+x["b"]} (field names without . and not in x,y,z) ..p.a+b+q.c → {[p0;x]p0+x["b"]+c}[a;] (p. projects; q. quotes) field expr. at x.. a+b → {x["a"]+x["b"]}[x] (same as (..a+b)x) dict fields ..[a:e1;b:e2;c] → "a""b""c"!(e1;e2;c) amend fields x..[a:e1;b:e2] → @[x;"a""b";:;x..(e1;e2)] cond ?[1;2;3] → 2 ?[0;2;3] → 3 ?[0;2;"";3;4] → 4 and/or and[1;2] → 2 and[1;0;3] → 0 or[0;2] → 2 or[0;0;0] → 0 return [1;:2;3] → 2 (a : at start of expression) try 'x is sugar for ?["e"~@x;:x;x] (return if it's an error) log \x logs a string representation of x (debug/display tool) discard `x discards well-formed x during parsing (ignore expression) comments from line with a single / until line with a single \ or from / (after space or start of line) to end of line TYPES HELP atom array name examples i I integer 0 -2 !5 4 3 -2 5 0i n N number 0.0 1.5 0.0+!5 1.2 3 0n 1e+10 s S string "abc" "d" "a" "b" "c" r regexp rx/[a-z]/ rx/\s+/ d dictionary "a""b"!1 2 keys!values f function + {x-1} 2* %[;2] h handle open"/path/to/file" "w"open"/path/to/file" e error error"msg" / file system dirfs"/path/to/dir" A generic array ("a" 1;"b" 2;"c" 3) (+;-;*;"any") VERBS HELP :x identity :[42] → 42 (recall that : is also syntax for return and assign) x:y right 2:3 → 3 "a":"b" → "b" +d swap k/v +"a""b"!0 1 → 0 1!"a" "b" +x flip +(1 2;3 4) → (1 3;2 4) +42 → ,,42 n+n add 2+3 → 5 2+3 4 → 5 6 s+s concat "a"+"b" → "ab" "a" "b"+"c" → "ac" "bc" -n negate - 2 3 → -2 -3 -(1 2.5;3 4) → (-1.0 -2.5;-3 -4) -s rtrim space -"a\tb \r\n" " c d \n" → "a\tb" " c d" (Unicode's White Space) n-n subtract 5-3 → 2 5 4-3 → 2 1 s-s trim suffix "file.txt"-".txt" → "file" *x first *7 8 9 → 7 *"ab" → "ab" *(+;*) → + n*n multiply 2*3 → 6 1 2 3*3 → 3 6 9 s*i repeat "a"*3 2 1 0 → "aaa" "aa" "a" "" %X classify %7 8 9 7 8 9 → 0 1 2 0 1 2 %"a" "b" "a" → 0 1 0 n%n divide 3%2 → 1.5 3 4%2 → 1.5 2.0 s%s glob match "*.csv"%"data.csv" "code.goal" "dir/data.csv" → 1 0 0 !i enum !5 → 0 1 2 3 4 !-5 → -5 -4 -3 -2 -1 !s fields !"a b\tc\nd \u00a0e" → "a""b""c""d""e" (Unicode's White Space) !I odometer !2 3 → (0 0 0 1 1 1;0 1 2 0 1 2) !d keys !"a""b"!1 2 → "a" "b" i!n mod/div 3!9 8 7 → 0 2 1 -3!9 8 7 → 3 2 2 i!s pad fields 3!"a" → "a " -3!"1" "23" "456" → " 1" " 23" "456" s!s fields ",;"!"a,b;c" → "a""b""c" (fields cut on any of ",;"; ""!s is !s) X!Y dict d:"a""b"!1 2; d"a" → 1 (same as d:..[a:1;b:2]; d..a) &s byte-count &"abc" → 3 &"π" → 2 &"αβγ" → 6 &I where &0 0 1 0 0 0 1 → 2 6 &2 3 → 0 0 1 1 1 &d keys where &"a""b""c""d"!0 1 1 0 → "b" "c" x&y min/and 2&3 → 2 4&3 → 3 "b"&"a" → "a" 0&1 → 0 |X reverse |!5 → 4 3 2 1 0 x|y max/or 2|3 → 3 4|3 → 4 "b"|"a" → "b" 0|1 → 1 <d sort up <"a""b""c"!2 3 1 → "c""a""b"!1 2 3 <X ascend <3 5 4 → 0 2 1 (index permutation for ascending order) x<y less 2<3 → 1 "c"<"a" → 0 7 8<6 9 → 0 1 >d sort down >"a""b""c"!2 3 1 → "b""a""c"!3 2 1 >X descend >3 5 4 → 1 2 0 (index permutation for descending order) x>y more 2>3 → 0 "c">"a" → 1 7 8>6 9 → 1 0 =s lines ="ab\ncd\r\nef gh" → "ab" "cd" "ef gh" =I index-count =1 0 0 2 2 3 -1 2 1 1 1 → 2 4 3 1 =d group keys ="a""b""c"!0 1 0 → ("a" "c";,"b") ="a""b"!0 -1 → ,,"a" f=Y group by (2!)=!10 → (0 2 4 6 8;1 3 5 7 9) x=y equal 2 3 4=3 → 0 1 0 "ab" = "ba" → 0 ~x not ~0 1 2 → 1 0 0 ~"a" "" "0" → 0 1 0 x~y match 3~3 → 1 2 3~3 2 → 0 ("a";%)~'("b";%) → 0 1 ,x enlist ,1 → ,1 #,2 3 → 1 (list with one element) d,d merge ("a""b"!1 2),"b""c"!3 4 → "a""b""c"!1 3 4 x,y join 1,2 → 1 2 "ab" "c","d" → "ab" "c" "d" ^d sort keys ^"c""a""b"!1 2 3 → "a""b""c"!2 3 1 ^X sort ^3 5 0 → 0 3 5 ^"ca" "ab" "bc" → "ab" "bc" "ca" i^s windows 2^"abcde" → "abcd" "bcde" i^Y windows 2^!4 → (0 1 2;1 2 3) -2^!4 → (0 1;1 2;2 3) s^s trim " #"^" #a ## b# " → "a ## b" ""^" \na\t b\t" → "a\t b" f^y weed out {0 1 1 0}^4 1 5 3 → 4 3 (0<)^2 -3 1 → ,-3 X^t w/o keys & (,"b";1 0)^..[a:6 7;b:8 9] → (,"a")!,,7 (0;..a>1;..b<0)^..[a:1 2 3;b:4 -5 6] → "a""b"!(,1;,4) X^d w/o keys (,"b")^"a""b""c"!0 1 2 → "a""c"!0 2 X^Y w/o values 2 3^1 1 2 3 3 4 → 1 1 4 (like in[;X]^Y) #x length #7 8 9 → 3 #"ab" "cd" → 2 #42 → 1 #"ab" → 1 i#y take/repeat 2#6 7 8 → 6 7 5#6 7 8 → 6 7 8 6 7 3#1 → 1 1 1 s#s count "ab"#"cabdab" "cd" "deab" → 2 0 1 ""#"αβγ" → 4 f#y replicate {0 1 2 0}#4 1 5 3 → 1 5 5 (0<)#2 -3 1 → 2 1 X#t w/ keys & (,"a";0 1)#..[a:6 7;b:8 9] → (,"a")!,,7 (1;..a>1;..b>0)#..[a:1 2 3;b:4 -5 6] → "a""b"!(,3;,6) X#d with keys "a""c""e"#"a""b""c""a"!2 3 4 5 → "a""c""a"!2 4 5 X#Y with values 2 3#1 1 2 3 3 4 → 2 3 3 (like in[;X]#Y) _n floor _2.3 → 2.0 _1.5 3.7 → 1.0 3.0 _s to lower _"ABC" → "abc" _"AB" "CD" "Π" → "ab" "cd" "π" i_s drop bytes 2_"abcde" → "cde" -2_"abcde" → "abc" i_Y drop 2_3 4 5 6 → 5 6 -2_3 4 5 6 → 3 4 s_s trim prefix "pfx-"_"pfx-name" "pfx2-name" → "name" "pfx2-name" f_Y cut where {0=3!x}_!10 → (0 1 2;3 4 5;6 7 8;,9) (same as (&f Y)_Y) I_s cut string 1 3_"abcdef" → "bc" "def" (I ascending) I_Y cut 2 5_!10 → (2 3 4;5 6 7 8 9) (I ascending) $x string $2 3 → "2 3" $"text" → "\"text\"" i$s cut shape 3$"abcdefghijk" → "abc" "defg" "hijk" i$Y cut shape 3$!6 → (0 1;2 3;4 5) -3$!6 → (0 1 2;3 4 5) s$y strings "s"$(1;"c";+) → "1""c""+" s$s chars/bytes "c"$"aπ" → 97 960 "b"$"aπ" → 97 207 128 s$i to string "c"$97 960 → "aπ" "b"$97 207 128 → "aπ" s$n cast "i"$2.3 → 2 @"n"$42 → "n" s$s parse i/n "i"$"42" "0b100" → 42 4 "n"$"2.5" "1e+20" → 2.5 1e+20 s$s parse value "v"$qq/(2 3;"a")/ → (2 3;"a") ($x inverse for types in "inrs") s$y format "%.2g"$1 4%3 → "0.33" "1.3" "%s=%03d"$"a" 42 → "a=042" X$y binsearch 2 3 5 7$8 2 7 5 5.5 3 0 → 4 1 4 3 3 2 0 (X ascending) ?i uniform ?2 → 0.6046602879796196 0.9405090880450124 (between 0 and 1) ?i normal ?-2 → -1.233758177597947 -0.12634751070237293 (mean 0, dev 1) ?X distinct ?2 2 4 3 2 3 → 2 4 3 (keeps first occurrences) i?i roll 5?100 → 10 51 21 51 37 i?Y roll array 5?"a" "b" "c" → "c" "a" "c" "c" "b" i?i deal -5?100 → 19 26 0 73 94 (always distinct) i?Y deal array -3?"a""b""c" → "a""c""b" (0i?Y is (-#Y)?Y) (always distinct) s?r rindex "abcde"?rx/b../ → 1 3 (offset;length) s?s index "a = a + 1"?"=" "+" → 2 6 d?y find key ("a""b"!3 4)?4 → "b" ("a" "b"!3 4)?5 → "" X?y find 9 8 7?8 → 1 9 8 7?6 → 3 @x type @2 → "i" @1.5 → "n" @"ab" → "s" @2 3 → "I" @(+) → "f" i@y take/pad 2@6 7 8 → 6 7 4@6 7 8 → 6 7 8 0 -4@6 7 8 → 0 6 7 8 s@i substr "abcdef"@2 → "cdef" (s[offset]) r@s match rx/^[a-z]+$/"abc" → 1 rx/\s/"abc" → 0 r@s find group rx/([a-z])(.)/"&a+c" → "a+" "a" "+" (whole match, group(s)) f@y apply at (|)@1 2 → 2 1 (like |[1 2] → 2 1 or |1 2 or (|).,1 2) d@y at key ..[a:6 7;b:8 9]"a" → 6 7 (1 2!"a""b")2 → "b" t@i at row ..[a:6 7;b:8 9]0 → "a""b"!6 8 X@i at 7 8 9@2 → 9 7 8 9[2 0] → 9 7 7 8 9@-2 → 8 .s get global a:3;."a" → 3 .e get error .error"msg" → "msg" .d values ."a""b"!1 2 → 1 2 .X self-dict ."a""b" → "a""b"!"a""b" .!3 → 0 1 2!0 1 2 s.I substr "abcdef"[2;3] → "cde" (s[offset;length]) r.y findN rx/[a-z]/["abc";2] → "a""b" rx/[a-z]/["abc";-1] → "a""b""c" r.y findN group rx/[a-z](.)/["abcdef";2] → ("ab" "b";"cd" "d") f.y apply (+).2 3 → 5 +[2;3] → 5 d.y deep at ..[a:6 7;b:8 9]["a";1] → 7 t.y at row;key ..[a:6 7;b:8 9][1;"a"] → (,"a")!,7 X.y deep at (6 7;8 9)[0;1] → 7 (6 7;8 9)[;1] → 7 9 «X shift «8 9 → 9 0 «"a" "b" → "b" "" (ASCII keyword: shift x) x«Y shift "a" "b"«1 2 3 → 3 "a" "b" »X rshift »8 9 → 0 8 »"a" "b" → "" "a" (ASCII keyword: rshift x) x»Y rshift "a" "b"»1 2 3 → "a" "b" 1 ::[s;y] set global ::["a";3];a → 3 (brackets needed because :: is monadic) @[d;y;f] amend @["a""b""c"!7 8 9;"a""b""b";10+] → "a""b""c"!17 28 9 @[X;i;f] amend @[7 8 9;0 1 1;10+] → 17 28 9 @[d;y;F;z] amend @["a""b""c"!7 8 9;"a";:;42] → "a""b""c"!42 8 9 @[X;i;F;z] amend @[7 8 9;1 2 0;+;10 20 -10] → -3 18 29 @[f;y;f] try at @[2+;"a";:] → "i+y : bad type \"s\" in y" (panic case) @[2+;3;:] → 5 (no-panic case) .[X;y;f] deep amend .[(6 7;8 9);0 1;-] → (6 -7;8 9) .[X;y;F;z] deep amend .[(6 7;8 9);(0 1 0;1);+;10] → (6 27;8 19) .[(6 7;8 9);(*;1);:;42] → (6 42;8 42) .[f;y;f] try .[+;2 "a";:] → "i+y : bad type \"s\" in y" (panic case) .[+;2 3;:] → 5 (no-panic case) NAMED VERBS HELP abs n abs value abs -3.0 -1.5 2.0 → 3.0 1.5 2.0 csv s csv read csv"a,b\n1,2" → ("a" "1";"b" "2") csv A csv write csv("a" "b";1 2) → "a,1\nb,2\n" error x error r:error"msg"; (@r;.r) → "e" "msg" eval s comp/run a:5;eval"a+2" → 7 (unrestricted variant of .s) firsts X mark firsts firsts 0 0 2 3 0 2 3 4 → 1 0 1 1 0 0 0 1 (same as ¿X) json s parse json json rq`{"a":true,"b":"text"}` → "a" "b"!0w "text" nan n isNaN nan(0n;2;sqrt -1) → 1 0 1 nan 2 0i 3 → 0 1 0 ocount X occur-count ocount 3 4 5 3 4 4 7 → 0 0 0 1 1 2 0 panic s panic panic"msg" (for fatal programming-errors) rx s comp. regex rx"[a-z]" (like rx/[a-z]/ but compiled at runtime) sign n sign sign -3 -1 0 1.5 5 → -1 -1 0 1 1 uc x upper/ceil uc 1.5 → 2.0 uc"abπ" → "ABΠ" s csv s csv read " "csv"a b\n1 2" → ("a" "1";"b" "2") (" " as separator) s csv A csv write " "csv("a" "b";1 2) → "a 1\nb 2\n" (" " as separator) x in s contained "bc" "ac"in"abcd" → 1 0 (same as x¿s) x in Y member of 2 3 in 8 2 4 → 1 0 (same as x¿Y) s json y write json ""json 1.5 2 → "[1.5,2]" (indent with s;disable with "") S json y write json like s json y, but with (pfx;indent) for pretty-printing n nan n fill NaNs 42.0 nan(1.5;sqrt -1) → 1.5 42.0 42 nan 2 0i → 2 42 i rotate Y rotate 2 rotate 7 8 9 → 9 7 8 -2 rotate 7 8 9 → 8 9 7 sub[r;s] regsub sub[rx/[a-z]/;"Z"] "aBc" → "ZBZ" sub[r;f] regsub sub[rx/[A-Z]/;_] "aBc" → "abc" sub[s;s] replace sub["b";"B"] "abc" → "aBc" sub[s;s;i] replaceN sub["a";"b";2] "aaa" → "bba" (stop after 2 times) sub[S] replaceS sub["b" "d" "c" "e"] "abc" → "ade" sub[S;S] replaceS sub["b" "c";"d" "e"] "abc" → "ade" eval[s;loc;pfx] like eval s, but provide loc as location (usually a path), and prefix pfx+"." for globals; does not eval same location more than once utf8 s is UTF-8 utf8 "aπc" → 1 utf8 "a\xff" → 0 s utf8 s to UTF-8 "b" utf8 "a\xff" → "ab" (replace invalid with "b") MATH: atan[n;n]; cos n; exp n; log n; round n; sin n; sqrt n ADVERBS HELP f'x each #'(4 5;6 7 8) → 2 3 x F'y each 2 3#'4 5 → (4 4;5 5 5) {(x;y;z)}'[1;2 3;4] → (1 2 4;1 3 4) x I'y case (6 7 8 9)0 1 0 1'"a""b""c""d" → 6 "b" 8 "d" I A'I at each m:3$!9;p:!2 2;(m').p → 0 1 3 4 x F`y eachleft 1 2,`"a""b" → (1 "a" "b";2 "a" "b") (same as F[;y]'x) x F´y eachright 1 2,´"a""b" → (1 2 "a";1 2 "b") (same as F[x;]'y) F/x fold +/!10 → 45 F\x scan +\!10 → 0 1 3 6 10 15 21 28 36 45 x F/y fold 5 6+/!4 → 11 12 {x+y-z}/[5;4 3;2 1] → 9 x F\y scan 5 6+\!4 → (5 6;6 7;8 9;11 12) {x+y-z}\[5;4 3;2 1] → 7 9 i f/y do 3(2*)/4 → 32 i f\y dos 3(2*)\4 → 4 8 16 32 f f/y while (100>)(2*)/4 → 128 f f\y whiles (100>)(2*)\4 → 4 8 16 32 64 128 f/x converge {1+1.0%x}/1 → 1.618033988749895 {-x}/1 → -1 f\x converges (-2!)\10 → 10 5 2 1 0 {-x}\1 → 1 -1 s/S join ","/"a" "b" "c" → "a,b,c" s\s split ","\"a,b,c" → "a" "b" "c" ""\"aπc" → "a" "π" "c" r\s split rx/[,;]/\"a,b;c,d" → "a" "b" "c" "d" i s\s splitN (2)","\"a,b,c" → "a" "b,c" i r\s splitN (3)rx/[,;]/\"a,b;c,d" → "a" "b" "c,d" I/x decode 24 60 60/1 2 3 → 3723 2/1 1 0 → 6 I\x encode 24 60 60\3723 → 1 2 3 2\6 → 1 1 0 TIME HELP time cmd time command with current time cmd time t time command with time t time[cmd;t;fmt] time command with time t in given format time[cmd;t;fmt;loc] time command with time t in given format and location Time t should consist either of integers or strings in the given format ("unix" is the default for integers and RFC3339 layout "2006-01-02T15:04:05Z07:00" is the default for strings), with optional location (default is "UTC"). See https://pkg.go.dev/time for information on layouts and locations, as Goal uses the same conventions as Go's time package. Supported values for cmd are as follows: cmd (s) result (type) fmt ------- ------------- --- "clock" hour, minute, second (I) "date" year, month, day (I) yes "day" day number (i) "hour" 0-23 hour (i) "minute" 0-59 minute (i) "month" 0-12 month (i) "second" 0-59 second (i) "unix" unix epoch time (i) yes "unixmicro" unix (microsecond version) (i) yes "unixmilli" unix (millisecond version) (i) yes "unixnano" unix (nanosecond version) (i) yes "week" year, week (I) "weekday" 0-7 weekday starting from Sunday (i) "year" year (i) "yearday" 1-365/6 year day (i) "zone" name, offset in seconds east of UTC (s;i) format (s) format time using given layout (s) yes RUNTIME HELP rt.get s returns various kinds of runtime information depending on s: "!" names of globals (S) "g" dict with copy of all globals (d) "f" same but only globals containing functions (d) "v" same but only non-function globals (d) rt.get["@";x] dict with internal info about x (for debug purposes only) rt.log x like :[x] but logs string representation of x (same as \x) rt.seed i set non-secure pseudo-rand seed to i (used by the ? verb) rt.time[s;i] eval s for i times (default 1), return average time (ns) rt.time[f;x;i] call f. x for i times (default 1), return average time (ns) rt.try[f;y;f] same as .[f;y;f] but the handler receives an error dict ..[msg:s;err:s] where msg contains the whole error stack trace IO/OS HELP chdir s change current working directory to s, or return an error close h flush any buffered data, then close handle h dirfs s return a read-only file system value, rooted at directory s, usable as left argument in glob, open, read, stat env s get environment variable s, or an error if unset return a dict representing the whole environment if s~"" flush h flush any buffered data for handle h glob s return file names matching glob pattern s import s read/eval wrapper roughly equivalent to eval[read path;path;pfx] where 1) path~s or path~env["GOALLIB"]+s+".goal" 2) pfx is path's basename without extension mkdir s create new directory named s (parent must already exist) open s open path s for reading, returning a handle (h) print s print"Hello, world!\n" (uses implicit $x for non-string values) read h read from handle h until EOF or an error occurs read s read file named s into string lines:=-read"/path/to/file" or dict ..[dir:I;name:S] if s is a directory remove s remove the named file or empty directory run s run command s or S (with arguments) run"pwd" run"ls" "-l" inherits stdin and stderr, returns its standard output or an error dict ..[msg:s;code:i;out:s] say s same as print, but appends a newline say!5 shell s same as run, but through "/bin/sh" (unix systems only) shell"ls -l" stat x returns dict ..[dir:i;mtime:i;size:i] (for filehandle h or path s) x env s set environment variable x to s, or return an error x env 0 unset environment variable x, or clear environment if x~"" x import s same as import s, but using prefix x for globals x open s open path s with mode x in "r" "w" "a" (file read/write/append) or pipe from or to command s or S with "pr" "pw" (pipe read/write) (synonymous modes: "<" ">" ">>" "-|" "|-") x print s print s to handle/name x "/path/to/file"print"content" i read h read i bytes from reader h or until EOF, or an error occurs s read h read from reader h until 1-byte s, EOF, or an error occurs x rename y renames (moves) old path x (s) to new path y (s) x run s same as run s but with input string x as stdin x say s same as print, but appends a newline ARGS command-line arguments, starting with script name STDIN standard input filehandle (buffered) STDOUT standard output filehandle (buffered) STDERR standard error filehandle (buffered)