#!/usr/bin/perl --
use strict; use warnings;
my $REint = qr{
#----------------------------------------------------------------------
  (?:                  #    group, but do not capture:
#----------------------------------------------------------------------
    (?:                #      group, but do not capture:
#----------------------------------------------------------------------
      [+-]?            #        any character of: '+', '-' (optional
                       #        (matching the most amount possible))
#----------------------------------------------------------------------
    )                  #      end of grouping
#----------------------------------------------------------------------
    (?:                #      group, but do not capture:
#----------------------------------------------------------------------
      [0123456789]+    #        any character of: '0', '1', '2', '3',
                       #        '4', '5', '6', '7', '8', '9' (1 or
                       #        more times (matching the most amount
                       #        possible))
#----------------------------------------------------------------------
    )                  #      end of grouping
#----------------------------------------------------------------------
  )                    #    end of grouping
#----------------------------------------------------------------------
}x; # end of qr

print "$_\n" for "1 plus 1 is 2" =~ m/$REint/g
__END__
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