in reply to REGEX Match Single Digit

YAPE::Regex::Explain is a handy tool to help you understand regular expressions: 
use strict;
use warnings;
use YAPE::Regex::Explain;

print YAPE::Regex::Explain->new('^\d[1]{1}$')->explain();

__END__

The regular expression:

(?-imsx:^\d[1]{1}$)

matches as follows:

NODE                     EXPLANATION
----------------------------------------------------------------------
(?-imsx:                 group, but do not capture (case-sensitive)
                         (with ^ and $ matching normally) (with . not
                         matching \n) (matching whitespace and #
                         normally):
----------------------------------------------------------------------
  ^                        the beginning of the string
----------------------------------------------------------------------
  \d                       digits (0-9)
----------------------------------------------------------------------
  [1]{1}                   any character of: '1' (1 times)
----------------------------------------------------------------------
  $                        before an optional \n, and the end of the
                           string
----------------------------------------------------------------------
)                        end of grouping
----------------------------------------------------------------------

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Re^2: REGEX Match Single Digit
by spickles (Scribe) on Aug 28, 2009 at 16:10 UTC
    That's cool. Thanks. From that output, am I understanding that one of my original attempts should have worked?
[reply]
      /\d1{1}/ matches any single decimal digit, "1" included, FOLLOWED BY a single "1".

      toolic's YAPE explanation makes that clear, but your original spec indicates you want a single digit (known in advance, I gather).

      Hence, /1{1}/ for a single "1" anywhere in a line, or /^1{1}$ for a line with a single "1" as its only content.

[reply]
[d/l]
[select]
      No
[reply]

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