... what do I call what I am trying to do with 0-9|a-e:0-9|a-e?

Assuming you're actually working with  [0-9]|[a-e]:[0-9]|[a-e] (please use  <code> ... </code> tags in future; please see Writeup Formatting Tips, Markup in the Monastery), it can be explained as: 

c:\@Work\Perl\monks>perl -wMstrict -le
"use YAPE::Regex::Explain;
 ;;
 my $rx = qr{ [0-9] | [a-e]:[0-9] | [a-e] }xms;
 print YAPE::Regex::Explain->new($rx)->explain;
"
The regular expression:

(?msx-i: [0-9] | [a-e]:[0-9] | [a-e] )

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):
----------------------------------------------------------------------
  [0-9]                    any character of: '0' to '9'
----------------------------------------------------------------------
 |                        OR
----------------------------------------------------------------------
  [a-e]                    any character of: 'a' to 'e'
----------------------------------------------------------------------
  :                        ':'
----------------------------------------------------------------------
  [0-9]                    any character of: '0' to '9'
----------------------------------------------------------------------
 |                        OR
----------------------------------------------------------------------
  [a-e]                    any character of: 'a' to 'e'
----------------------------------------------------------------------
)                        end of grouping
----------------------------------------------------------------------

[download]
See YAPE::Regex::Explain for regexes of Perl version 5.6 or before.

Give a man a fish:  <%-(-(-(-<

In reply to Re^3: remove lines that do not match search pattern by AnomalousMonk
in thread remove lines that do not match search pattern by jasonwolf

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