the match operator is documented in perlop, and regular expressions are documented in perlre, perlretut... Read perlintro

use YAPE::Regex::Explain;
print YAPE::Regex::Explain->new(qr/^\.{1,2}$/)->explain;
__END__
The regular expression:

(?-imsx:^\.{1,2}$)

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
----------------------------------------------------------------------
  \.{1,2}                  '.' (between 1 and 2 times (matching the
                           most amount possible))
----------------------------------------------------------------------
  $                        before an optional \n, and the end of the
                           string
----------------------------------------------------------------------
)                        end of grouping
----------------------------------------------------------------------
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