where will make install place the .pl file?

As always it depends. If you do nothing and have used h2xs to build your skeleton it will simply get dumped in the same location as your .pm files. To install a .pl script (say it is at DISTRO/bin/foo.pl in your distro) into a bin dir you modify the Makefile.PL like this:

use ExtUtils::MakeMaker;

WriteMakefile(
    'NAME'              => 'Foo',
    'VERSION_FROM'      => 'Foo.pm',
    'EXE_FILES'         => ['bin/foo.pl'], # <--- Add list of .pl exe 
+files to install
);
[download]

The foo.pl script will now be installed in an architecture dependent bin dir. This will proabably allow the user to just type foo.pl as it will *probably* be in their path. On win32 a .bat file will also be automatically generated. You can control the install location with perl Makefile.PL PREFIX=blah This affects both .pm and exe_files. LIB controls compiled binary install location if you have C/XS code.