diff --git a/Makefile b/Makefile
index 39270b578..f2f55ce01 100644
--- a/Makefile
+++ b/Makefile
@@ -57,12 +57,22 @@ bench-input:
 regression-test:
 	go test -v regression_test.go
 
+# ----------------------------------------------------------------
+# Experimental executables:
+scan:
+	go build github.com/johnkerl/miller/cmd/scan
+
+# ----------------------------------------------------------------
+# Formatting
 # go fmt ./... finds experimental C files which we want to ignore.
 fmt:
 	-go fmt ./cmd/...
 	-go fmt ./internal/pkg/...
 	-go fmt ./regression_test.go
 
+# ----------------------------------------------------------------
+# Static analysis
+
 # Needs first: go install honnef.co/go/tools/cmd/staticcheck@latest
 # See also: https://staticcheck.io
 staticcheck:
@@ -109,4 +119,4 @@ release_tarball: build check
 
 # ================================================================
 # Go does its own dependency management, outside of make.
-.PHONY: build mlr check unit_test regression_test bench fmt staticcheck dev docs
+.PHONY: build mlr scan check unit_test regression_test bench fmt staticcheck dev docs
diff --git a/cmd/scan/main.go b/cmd/scan/main.go
new file mode 100644
index 000000000..343465011
--- /dev/null
+++ b/cmd/scan/main.go
@@ -0,0 +1,338 @@
+// ================================================================
+// Experiments for type-inference performance optimization
+// ================================================================
+
+package main
+
+import (
+	"fmt"
+	"os"
+	"runtime"
+	"runtime/debug"
+	"runtime/pprof"
+	"strconv"
+
+	"github.com/pkg/profile" // for trace.out
+)
+
+type tScanType int
+
+const (
+	scanTypeString     tScanType = 0
+	scanTypeDecimalInt           = 1
+	scanTypeOctalInt             = 2
+	scanTypeHexInt               = 3
+	scanTypeBinaryInt            = 4
+	scanTypeMaybeFloat           = 5
+	scanTypeBool                 = 6
+)
+
+var scanTypeNames = []string{
+	"string",
+	"decint",
+	"octint",
+	"hexint",
+	"binint",
+	"float?",
+	"bool",
+}
+
+// 00000000: 00 01 02 03  04 05 06 07  08 09 0a 0b  0c 0d 0e 0f |................|
+// 00000010: 10 11 12 13  14 15 16 17  18 19 1a 1b  1c 1d 1e 1f |................|
+// 00000020: 20 21 22 23  24 25 26 27  28 29 2a 2b  2c 2d 2e 2f | !"#$%&'()*+,-./|
+// 00000030: 30 31 32 33  34 35 36 37  38 39 3a 3b  3c 3d 3e 3f |0123456789:;<=>?|
+// 00000040: 40 41 42 43  44 45 46 47  48 49 4a 4b  4c 4d 4e 4f |@ABCDEFGHIJKLMNO|
+// 00000050: 50 51 52 53  54 55 56 57  58 59 5a 5b  5c 5d 5e 5f |PQRSTUVWXYZ[\]^_|
+// 00000060: 60 61 62 63  64 65 66 67  68 69 6a 6b  6c 6d 6e 6f |`abcdefghijklmno|
+// 00000070: 70 71 72 73  74 75 76 77  78 79 7a 7b  7c 7d 7e 7f |pqrstuvwxyz{|}~.|
+
+var isDecimalDigitTable = []bool{
+	false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, // 00-0f
+	false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, // 10-1f
+	false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, // 20-2f
+	true, true, true, true, true, true, true, true, true, true, false, false, false, false, false, false, // 30-3f
+	false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, // 40-4f
+	false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, // 50-5f
+	false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, // 60-6f
+	false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, // 70-7f
+}
+
+var isHexDigitTable = []bool{
+	false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, // 00-0f
+	false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, // 10-1f
+	false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, // 20-2f
+	true, true, true, true, true, true, true, true, true, true, false, false, false, false, false, false, // 30-3f
+	false, true, true, true, true, true, true, false, false, false, false, false, false, false, false, false, // 40-4f
+	false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, // 50-5f
+	false, true, true, true, true, true, true, false, false, false, false, false, false, false, false, false, // 60-6f
+	false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, // 70-7f
+}
+
+// Possible character in floats include '.', 0-9, [eE], [-+] -- the latter two for things like 1.2e-8.
+// Miller intentionally does not accept 'inf' or 'NaN' as float numbers in file-input data.
+var isFloatDigitTable = []bool{
+	false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, // 00-0f
+	false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, // 10-1f
+	false, false, false, false, false, false, false, false, false, false, false, true, false, true, true, false, // 20-2f
+	true, true, true, true, true, true, true, true, true, true, false, false, false, false, false, false, // 30-3f
+	false, false, false, false, false, true, false, false, false, false, false, false, false, false, false, false, // 40-4f
+	false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, // 50-5f
+	false, false, false, false, false, true, false, false, false, false, false, false, false, false, false, false, // 60-6f
+	false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, // 70-7f
+}
+
+func isDecimalDigit(c byte) bool {
+	if c < 128 { // byte is unsigned in Go
+		return isDecimalDigitTable[c]
+	} else {
+		return false
+	}
+}
+
+func isHexDigit(c byte) bool {
+	if c < 128 { // byte is unsigned in Go
+		return isHexDigitTable[c]
+	} else {
+		return false
+	}
+}
+
+func isFloatDigit(c byte) bool {
+	if c < 128 { // byte is unsigned in Go
+		return isFloatDigitTable[c]
+	} else {
+		return false
+	}
+}
+
+// ----------------------------------------------------------------
+
+// TODO: UT the type-names LUT
+// TODO: inout tabls & CLI access & UT access & bench access
+
+func findScanType(input []byte) tScanType {
+	if len(input) == 0 {
+		return scanTypeString
+	}
+
+	i0 := input[0]
+	if i0 == '-' {
+		return findScanTypePositiveNumberOrString(input[1:])
+	}
+	if i0 >= '0' && i0 <= '9' {
+		return findScanTypePositiveNumberOrString(input)
+	}
+	if i0 == '.' {
+		return findScanTypePositiveDecimalOrFloatOrString(input)
+	}
+
+	sinput := string(input)
+	if sinput == "true" || sinput == "false" {
+		return scanTypeBool
+	}
+
+	return scanTypeString
+}
+
+// TODO: type up the why
+//  o make a grammar for numbers & case-through
+//    k len 0
+//    - len 1
+//    k has leading minus; strip & rest
+//    - 0x, 0b, 0[0-9]
+//    - decimal: leading minus; [0-9]+
+//    - octal:   leading minus; 0[0-7]+
+//    - hex:     leading minus; 0[xX][0-9a-fA-F]+
+//    - float:   leadinug minus; [0-9] or '.'
+//
+//  o float literals:
+//    123 123.  123.4 .234
+//    1e2 1e-2 1.2e3 1.e3 1.2e-3 1.e-3
+//    .2e3 .2e-3 1.e-3
+//
+//    ?- [0-9]+
+//    ?- [0-9]+ '.' [0-9]*
+//    ?- [0-9]* '.' [0-9]+
+//    ?- [0-9]+            [eE] ?- [0-9]+
+//    ?- [0-9]+ '.' [0-9]* [eE] ?- [0-9]+
+//    ?- [0-9]* '.' [0-9]+ [eE] ?- [0-9]+
+
+func findScanTypePositiveNumberOrString(input []byte) tScanType {
+	if len(input) == 0 {
+		return scanTypeString
+	}
+	i0 := input[0]
+
+	if i0 == '.' {
+		return findScanTypePositiveFloatOrString(input)
+	}
+
+	if isDecimalDigit(i0) {
+		if len(input) == 1 {
+			return scanTypeDecimalInt
+		}
+		if i0 == '0' {
+			i1 := input[1]
+			if i1 == 'x' || i1 == 'X' {
+				return findScanTypePositiveHexOrString(input[2:])
+			}
+			if i1 == 'b' || i1 == 'B' {
+				return findScanTypePositiveBinaryOrString(input[2:])
+			}
+		}
+
+		// TODO: nope, could be float too
+		return findScanTypePositiveDecimalOrFloatOrString(input)
+	}
+
+	return scanTypeString
+}
+
+func findScanTypePositiveFloatOrString(input []byte) tScanType {
+	for _, c := range []byte(input) {
+		if !isFloatDigit(c) {
+			return scanTypeString
+		}
+	}
+	return scanTypeMaybeFloat
+}
+
+func findScanTypePositiveDecimalOrFloatOrString(input []byte) tScanType {
+	maybeInt := true
+	for _, c := range []byte(input) {
+		// All float digits are decimal-int digits so if the current character
+		// is not a float digit, this can't be either a float or a decimal int.
+		// Example: "1x2"
+		if !isFloatDigit(c) {
+			return scanTypeString
+		}
+
+		// Examples: "1e2" or "1x2".
+		if !isDecimalDigit(c) {
+			maybeInt = false
+		}
+	}
+	if maybeInt {
+		return scanTypeDecimalInt
+	} else {
+		return scanTypeMaybeFloat
+	}
+}
+
+// Leading 0x has already been stripped
+func findScanTypePositiveHexOrString(input []byte) tScanType {
+	for _, c := range []byte(input) {
+		if !isHexDigit(c) {
+			return scanTypeString
+		}
+	}
+	return scanTypeHexInt
+}
+
+// Leading 0b has already been stripped
+func findScanTypePositiveBinaryOrString(input []byte) tScanType {
+	for _, c := range []byte(input) {
+		if c < '0' || c > '1' {
+			return scanTypeString
+		}
+	}
+	return scanTypeBinaryInt
+}
+
+// ----------------------------------------------------------------
+func scanMain() {
+
+	//	var c byte
+	//
+	//	fmt.Printf("dec: ")
+	//	for c = 0x20; c <= 0x6f; c++ {
+	//		if isDecimalDigit(c) {
+	//			fmt.Printf("%c", c)
+	//		}
+	//	}
+	//	fmt.Println()
+	//
+	//	fmt.Printf("hex: ")
+	//	for c = 0x20; c <= 0x6f; c++ {
+	//		if isHexDigit(c) {
+	//			fmt.Printf("%c", c)
+	//		}
+	//	}
+	//	fmt.Println()
+	//
+	//	fmt.Printf("float: ")
+	//	for c = 0x20; c <= 0x6f; c++ {
+	//		if isFloatDigit(c) {
+	//			fmt.Printf("%c", c)
+	//		}
+	//	}
+	//	fmt.Println()
+
+	// TODO:
+	// func ParseInt(s string, base int, bitSize int) (int64, error)
+	// func ParseUint(s string, base int, bitSize int) (uint64, error)
+
+	for _, arg := range os.Args[1:] {
+		scanType := findScanType([]byte(arg))
+		fmt.Printf("%-10s -> %s\n", arg, scanTypeNames[scanType])
+	}
+}
+
+// ----------------------------------------------------------------
+func main() {
+
+	// Respect env $GOMAXPROCS, if provided, else set default.
+	haveSetGoMaxProcs := false
+	goMaxProcsString := os.Getenv("GOMAXPROCS")
+	if goMaxProcsString != "" {
+		goMaxProcs, err := strconv.Atoi(goMaxProcsString)
+		if err != nil {
+			runtime.GOMAXPROCS(goMaxProcs)
+			haveSetGoMaxProcs = true
+		}
+	}
+	if !haveSetGoMaxProcs {
+		// As of Go 1.16 this is the default anyway. For 1.15 and below we need
+		// to explicitly set this.
+		runtime.GOMAXPROCS(runtime.NumCPU())
+	}
+
+	debug.SetGCPercent(500) // Empirical: See README-profiling.md
+
+	//  - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+	// CPU profiling
+	//
+	// We do this here, not in the command-line parser, since
+	// pprof.StopCPUProfile() needs to be called at the very end of everything.
+	// Putting this pprof logic into a go func running in parallel with main,
+	// and properly stopping the profile only when main ends via chan-sync,
+	// results in a zero-length pprof file.
+	//
+	// Please see README-profiling.md for more information.
+
+	if len(os.Args) >= 3 && os.Args[1] == "--cpuprofile" {
+		profFilename := os.Args[2]
+		handle, err := os.Create(profFilename)
+		if err != nil {
+			fmt.Fprintln(os.Stderr, os.Args[0], ": ", "Could not start CPU profile: ", err)
+			return
+		}
+		defer handle.Close()
+
+		if err := pprof.StartCPUProfile(handle); err != nil {
+			fmt.Fprintln(os.Stderr, os.Args[0], ": ", "Could not start CPU profile: ", err)
+			return
+		}
+		defer pprof.StopCPUProfile()
+
+		fmt.Fprintf(os.Stderr, "CPU profile started.\n")
+		defer fmt.Fprintf(os.Stderr, "CPU profile finished.\ngo tool pprof -http=:8080 %s\n", profFilename)
+	}
+
+	if len(os.Args) >= 3 && os.Args[1] == "--traceprofile" {
+		defer profile.Start(profile.TraceProfile, profile.ProfilePath(".")).Stop()
+		defer fmt.Fprintf(os.Stderr, "go tool trace trace.out\n")
+	}
+
+	scanMain()
+}
diff --git a/todo.txt b/todo.txt
index 672dfbd1b..1e0c04bcf 100644
--- a/todo.txt
+++ b/todo.txt
@@ -2,6 +2,7 @@
 PUNCHDOWN LIST
 
 * blockers:
+  ! .mlrrc suppress
   - linux/1.17 perf checks
   - fractional-strptime
   - improved regex doc w/ lots of examples
@@ -16,9 +17,12 @@ PUNCHDOWN LIST
 * numeric-inference perf
   o README-profiling.md re various scripts
   o https://stackoverflow.com/questions/64513411/why-is-strconv-parseuint-so-slow-compared-to-strconv-atoi
-  o benchmark per se
-  o reconsider TryInt/TryFloat -> maybe try number -- ?
+  k benchmark per se
+  o mlr --time
+  o try traceprofile?
+  o find a second linux machine to check -- ?
   o get octal regexp out of hot path
+
   o make a grammar for numbers & case-through
     - len 0
     - len 1