Ok, this groups  -sub_args -cd together:

c:\@Work\Perl\monks>perl -wMstrict -le
"$_ = q(execute test_number_1 -tex -tex_args -sub_args +debug_dir=./ -
+sub_args +debug_dir=./ -constraint parity_en,random_en -sub_args '\"'
+ ruck=1 '\"' -constraint dual_en -sub_args -cd -sub_args 2596.slow -s
+ub_args test -seed 1 -tex_args- -opt 1 -tag 2);
 ;;
 print qq{>$_< \n};
 ;;
 # my $sw = qr{ (?: -sub_args \s+ \S+ | \S) .*? }xms;
 my $chunk = qr{ (?: -sub_args \s+ \S+ | \S) .*? (?= \s+ - | \Z) }xms;
 my $answer;
 $answer .= s/^-/\t-/gmr . qq{\n} for /$chunk/g;
 $answer =~ s{^(\s*)(-\w+)\n\K((?:.*\n)*?)(?=\1\2-\n)}
             { $3 =~ s{^}{\t}gmr }gem;
 ;;
 print qq{>>>$answer<<< \n};
"
>execute test_number_1 -tex -tex_args -sub_args +debug_dir=./ -sub_arg
+s +debug_dir=./ -constraint parity_en,random_en -sub_args '"' ruck=1 
+'"' -constraint dual_en -sub_args -cd -sub_args 2596.slow -sub_args t
+est -seed 1 -tex_args- -opt 1 -tag 2<

>>>execute test_number_1
        -tex
        -tex_args
                -sub_args +debug_dir=./
                -sub_args +debug_dir=./
                -constraint parity_en,random_en
                -sub_args '"' ruck=1 '"'
                -constraint dual_en
                -sub_args -cd
                -sub_args 2596.slow
                -sub_args test
                -seed 1
        -tex_args-
        -opt 1
        -tag 2
<<<
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Update: The
    my $sw = qr{ (?: -sub_args \s+ \S+ | \S) .*? }xms;
statement above is superfluous.