How to track the execution of regular expressions?

use re'debug'; 

my $str = "abcdefg";
$str =~ m/[ef]+/;

Compiling REx "[ef]+"
Final program :
 1: PLUS (13)
 2: ANYOF[ef] (0)
 13: END (0)
stclass ANYOF[ef] plus minlen 1 
 Matching REx "[ef]+" against "abcdefg"
Matching stclass ANYOF[ef] against "abcdefg" (7 bytes)
 4   | 1:PLUS(13)
 ANYOF[ef] can match 2 times out of 2147483647...
 6   | 13: END(0)
Match successful!
Freeing REx: "[ ef]+"

Is there a convenient way to get the status of the regular expression engine when evaluating m // or s /// expressions?

By the way, I know that the Regexp::Debugger package is available through CPAN (and very cool), but I have no way to get any similar traces from it; I don’t want to gradually complete a large number of Steps.

Yes. Turn the regular expression engine into debug mode, and it will print what it is doing:

use re'debug'; 

my $str = "abcdefg";
$str =~ m/[ef]+/;

This gives an output:

Compiling REx "[ef]+"
Final program:
 1: PLUS (13)< br /> 2: ANYOF[ef] (0)
 13: END (0)
stclass ANYOF[ef] plus minlen 1 
Matching REx "[ef]+" against "abcdefg" 
Matching stclass ANYOF[ef] against "abcdefg" (7 bytes)
 4   | 1:PLUS(13)
 ANYOF[ef] can match 2 times out of 2147483647...
 6   | 13: END(0)
Match successful!
Freeing REx: "[ef]+"