c:\@Work\Perl\monks>perl -wMstrict -le
"use YAPE::Regex::Explain;
 ;;
 print YAPE::Regex::Explain->new(qr{ (?: [|] [^|]*){4} \z }xms)->explain;
"
The regular expression:

(?msx-i: (?: [|] [^|]*){4} \z )

matches as follows:

NODE                     EXPLANATION
----------------------------------------------------------------------
(?msx-i:                 group, but do not capture (with ^ and $
                         matching start and end of line) (with .
                         matching \n) (disregarding whitespace and
                         comments) (case-sensitive):
----------------------------------------------------------------------
  (?:                      group, but do not capture (4 times):
----------------------------------------------------------------------
    [|]                      any character of: '|'
----------------------------------------------------------------------
    [^|]*                    any character except: '|' (0 or more
                             times (matching the most amount
                             possible))
----------------------------------------------------------------------
  ){4}                     end of grouping
----------------------------------------------------------------------
  \z                       the end of the string
----------------------------------------------------------------------
)                        end of grouping
----------------------------------------------------------------------