The DEBUG=$DEBUG ensures that DEBUG exists in the environment for the awk.
But it's pure overhead if it was already in the shell's environment.
You can achieve the same with an exported variable (exported = placed in the shell's environment)
Because DEBUG is in the shell's environment, all the run commands inherit it.
The use of ENVIRON[ ] in an awk script is interesting. Thanks for sharing!
It is not used often. Reason: when awk is run from the shell there is easy passing of variables.
The Posix style:
Or the (bit dirty) Unix awk style
Either invocation sets the DEBUG variable in awk, so there is no need for pulling it from ENVIRON[ ]
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LEARN ABOUT MOJAVE
english5.18
English(3pm) Perl Programmers Reference Guide English(3pm)NAME
English - use nice English (or awk) names for ugly punctuation variables
SYNOPSIS
use English;
use English qw( -no_match_vars ) ; # Avoids regex performance penalty
# in perl 5.16 and earlier
...
if ($ERRNO =~ /denied/) { ... }
DESCRIPTION
This module provides aliases for the built-in variables whose names no one seems to like to read. Variables with side-effects which get
triggered just by accessing them (like $0) will still be affected.
For those variables that have an awk version, both long and short English alternatives are provided. For example, the $/ variable can be
referred to either $RS or $INPUT_RECORD_SEPARATOR if you are using the English module.
See perlvar for a complete list of these.
PERFORMANCE
NOTE: This was fixed in perl 5.20. Mentioning these three variables no longer makes a speed difference. This section still applies if
your code is to run on perl 5.18 or earlier.
This module can provoke sizeable inefficiencies for regular expressions, due to unfortunate implementation details. If performance matters
in your application and you don't need $PREMATCH, $MATCH, or $POSTMATCH, try doing
use English qw( -no_match_vars ) ;
. It is especially important to do this in modules to avoid penalizing all applications which use them.
perl v5.18.2 2014-01-06 English(3pm)