Re^3: Die vs. Exit

I'm having trouble figuring out the regular expression for integers, positive or negative?

/^-?\d+$/
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Can someone please explain what the characters mean? I may have better luck figuring it out with a good explanation? Thanks!

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Re^4: Die vs. Exit by kcott (Archbishop) on Jul 21, 2012 at 01:02 UTC
YAPE::Regex::Explain provides a good explanation: $ perl -E ' use YAPE::Regex::Explain; my $e = YAPE::Regex::Explain->new(q{^-?\d+$})->explain; say $e; ' The regular expression: (?-imsx:^-?\d+$) 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 ---------------------------------------------------------------------- -? '-' (optional (matching the most amount possible)) ---------------------------------------------------------------------- \d+ digits (0-9) (1 or more times (matching the most amount possible)) ---------------------------------------------------------------------- $ before an optional \n, and the end of the string ---------------------------------------------------------------------- ) end of grouping ---------------------------------------------------------------------- [download] I'd also recommend the following documentation: perlrequick - Perl regular expressions quick start perlretut - Perl regular expressions tutorial perlre - Perl regular expressions -- Ken	[reply] [d/l]

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Re^4: Die vs. Exit
by kcott (Archbishop) on Jul 21, 2012 at 01:02 UTC

YAPE::Regex::Explain provides a good explanation:

$ perl -E '
use YAPE::Regex::Explain;
my $e = YAPE::Regex::Explain->new(q{^-?\d+$})->explain;
say $e;
'
The regular expression:

(?-imsx:^-?\d+$)

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
----------------------------------------------------------------------
  -?                       '-' (optional (matching the most amount
                           possible))
----------------------------------------------------------------------
  \d+                      digits (0-9) (1 or more times (matching
                           the most amount possible))
----------------------------------------------------------------------
  $                        before an optional \n, and the end of the
                           string
----------------------------------------------------------------------
)                        end of grouping
----------------------------------------------------------------------
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I'd also recommend the following documentation:

perlrequick - Perl regular expressions quick start
perlretut - Perl regular expressions tutorial
perlre - Perl regular expressions

-- Ken

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