perldoc -lf whatever
[download]

$ perldoc -lf anomaly
/home/choroba/localperl/lib/5.43.9/pod/perlfunc.pod
/home/choroba/localperl/lib/5.43.9/pod/perlop.pod
[download]

returns perlfunc and perlop regardless of what "whatever" is.

$ perldoc -lf anomaly
/home/choroba/localperl/lib/5.43.9/pod/perlfunc.pod
/home/choroba/localperl/lib/5.43.9/pod/perlop.pod

Thanks for looking into it choroba. These results clearly contradict the perldoc documentation:

perldoc perldoc (and man perldoc) says:
-l   Display only the file name of the module found.

perldoc --help says:
-l   Display the module's file name

Here's another anomaly:

% perldoc -lf splice    
/Users/u/perl5/perlbrew/perls/perl-5.42.0/lib/5.42.0/pods/perlfunc.pod
/Users/u/perl5/perlbrew/perls/perl-5.42.0/lib/5.42.0/pods/perlop.pod

% perldoc $_        
No documentation found for "splice".

% perldoc -v $_
'splice' does not look like a Perl variable

% perldoc -v '$_'
$_      The default input and pattern-searching space...

And another one:

% perldoc -v '$_'
$_      The default input and pattern-searching space...

% perldoc -v '@_' 
@_      Within a subroutine the array @_ contains the parameters...

% perldoc -v '%_'
No documentation for perl variable '%_' found

I'm not sure about the "another anomaly". You get the documentation of splice for $_, as $_ without quotes is the shell variable which contains the last argument of the last command.
map{substr$_->[0],$_->[1]||0,1}[\*||{},3],[[]],[ref qr-1,-,-1],[{}],[sub{}^*ARGV,3]

These results clearly contradict the perldoc documentation:

That's not true. The docs don't say what happens if you use -l with -f func instead of a module.

Here's another anomaly

What do you think is anomalous? That it's looking up splice instead of $_? That's your error. You interpolated shell variable $_ into your shell command, and it apparently had the value splice.

And another one:

What do you think is anomalous? That output is correct too, and I have no idea what you think is wrong.

These results clearly contradict the perldoc documentation:

That's not true. The docs don't say what happens if you use -l with -f func instead of a module.

Here's another anomaly

What do you think is anomalous? That it's looking up splice instead of $_? That's your error. You interpolated shell variable $_ into your shell command, and it apparently had the value splice.

And another one:

What do you think is anomalous? That output is correct too, and I have no idea what you think is wrong.

What do you expect -lf to produce???

If anything this undefined behaviour should be rejected.

Anyway my best guess is that

• -f is always (only) searching those two docs for snippets
• -l is always listing the full path of parsed pods

So this "anomaly" makes IMHO perfect sense.

Edit

Usage demo

$ perldoc -l perldoc
/data/data/com.termux/files/usr/lib/perl5/5.40.3/pod/perldoc.pod
$ perldoc -l Data::Dumper
/data/data/com.termux/files/usr/lib/perl5/5.40.3/aarch64-android/Data/
+Dumper.pm
$ perldoc -f x
    x
    xor     These operators are documented in perlop.

$
[download]

Update

If your intention was to find every perldoc documenting a certain keyword :

I once wrote a script which will parse them all for X<keyword> tags.

See Perldoc Keyword Search (update3)