The name DEBUG_REGEX is made up, and can be anything (note the test of $ENV{DEBUG_REGEX} in the code).

How about:

my $re1 = qr/a/;
my $re2 = do { use if $ENV{FOO_DEBUG_REGEX},
    qw/re Debug EXECUTE/; qr/b/ };
my $re3 = qr/c/;
my $str = "ab";
$str =~ $re1;
$str =~ $re2;
$str =~ $re3;

[download]

will output run-time debug info on $re2 only when the environment var FOO_DEBUG_REGEX is set.

I'm not sure if this can be done dynamically in the debugger, perhaps another monk with more experience there can help. The documentation does say that use re 'debug'; has both compile-time and run-time effects.

In reply to Re^4: Turning on regexp debugging at runtime by Anonymous Monk
in thread Turning on regexp debugging at runtime by SBECK

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