I get a warning for FL2 Scalar value @row[FL2] better written as $row[FL2] (ignoring that its a constant _list_)
$ ./Porting/bisect.pl --target=miniperl --start=v5.16.3 --end=v5.26.0 
+--expect-fail -e 'use warnings FATAL=>"all"; sub X () {2,3}; my @a=("
+a".."z"); print @a[X]'
...
commit 429a25554a608b64c0ee46c1ffe19bab3718a3c8
Author: Father Chrysostomos <sprout@cpan.org>
Date:   Sat Sep 14 17:23:11 2013 -0700

    Reduce false positives for @hsh{$s} and @ary[$s] warnings
    
    This resolves tickets #28380 and #114024.
    
    Commit 95a31aad5 did something similar to this for the new %hash{.
+..}
    syntax.  This commit extends it to @ slices and combines the two
    code paths.
    
    The heuristics in toke.c can easily produce false positives.  So t
+he
    op is flagged as being a candidate for the warning.  Then when op.
+c
    has the op tree available, it examines it to see whether the heuri
+stic
    may have been a false positive.
    
    This avoids bugs with qw "foo bar baz" and sub calls triggering
    the warning.
    
    The source code is no longer available for the warning, so we reco
+n-
    struct it from the op tree, skipping the subscript if it is anythi
+ng
    other than a const op.
    
    This means that @hash{$foo} comes out as @hash{...} and @hash{foo}
+ as
    @hash{"foo"}.  It also meeans that @hash{"]"} is displayed correct
+ly
    instead of as @hash{"].
    
    Commit 95a31aad5 also modified the heuristic for %hash{...} to exe
+mpt
    qw altogether.  But it did not exempt it if it was preceded by a t
+ab.
    So this commit rectifies that.
    
    This commit also improves the false positive detection by exemptin
+g
    any ops returning lists that can get past toke.c’s heuristic.  I w
+ent
    through the entire list of ops, but I may have missed some.
    
    Also, @ slices on the lhs of = are exempt, as they change the cont
+ext
    and are hence actually useful.

$ git tag --contains 429a25554a608b6
... v5.20.0 ...

[download]
Deparsing the code shows that FL and FL2 are called as functions @a[FL()] = @row[FL2()];
$ ./Porting/bisect.pl --start=v5.16.3 --end=v5.26.0 -e '`$^X -Ilib -MO
+=Deparse -e "use constant X=>3,4; \@x[X]"`=~/\@x\[3, 4\]/ and die'
...
commit f815dc14d7c5540dfb5d02d001e0101c6266f281
Author: Father Chrysostomos <sprout@cpan.org>
Date:   Sun Jun 30 00:20:33 2013 -0700

    Inline list constants
    
    These are inlined the same way as 1..5.  We have two ops:
    
      rv2av
        |
        `-- const
    
    The const op returns an AV, which is stored in the op tree, and th
+en
    rv2av flattens it.

$ git tag --contains f815dc14d7c5540d
... v5.20.0 ...

# *Update:* making sure it's not just the Deparse output that changed.
+..
$ ./Porting/bisect.pl --start=v5.19.0 --end=v5.21.0 -e '`$^X -Ilib -MO
+=Concise -e "use constant X=>3,4; \@x[X]"`=~/entersub/ or die'
...
commit f815dc14d7c5540dfb5d02d001e0101c6266f281

[download]

In reply to Re: Constants lists in array slices by haukex
in thread Constants lists in array slices by LanX

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