[DOC PATCH bleadperl] Document underscores in numeric literals

Message-ID: <3AE9A0ED.5248.CEA127@localhost>

p4raw-id: //depot/perl@9884

1 files changed, 13 insertions, 1 deletions

diff --git a/pod/perldata.pod b/pod/perldata.pod
index 315f716ed8..48cd0e7cf5 100644
--- a/pod/perldata.pod
+++ b/pod/perldata.pod
@@ -271,11 +271,23 @@ integer formats:
     12345
     12345.67
     .23E-10             # a very small number
-    4_294_967_296       # underline for legibility
+    4_294_967_296       # underscore for legibility
     0xff                # hex
     0377                # octal
     0b011011            # binary
 
+You are allowed to use an underscore in numeric literals for legibility,
+but in decimal numeric literals (those written in base 10, not
+necessarily with a fractional part), digits may only be grouped in
+threes. For decimal numeric literals containing a fractional part,
+this applies only to the part before the decimal point; the fractional
+part (but not the exponent, if given!) may contain underscores
+anywhere you feel it enhances legibility. Binary, octal, and
+hexadecimal numeric literals may contain underscores in any place --
+so you could, for example, group binary digits by threes (as for a
+Unix-style mode argument such as 0b110_100_100) or by fours (to
+represent nibbles, as in 0b1010_0110) or in other groups.
+
 String literals are usually delimited by either single or double
 quotes.  They work much like quotes in the standard Unix shells:
 double-quoted string literals are subject to backslash and variable