From perllocale:

By default, Perl ignores the current locale. The "use locale" pragma tells Perl to use the current locale for some operations: [ ... ] lc().

$ perl -le 'print lc "ÄÖÜ";'
ÄÖÜ

$ echo $LC_ALL
de_DE

$ perl -Mlocale -le 'print lc "ÄÖÜ";'
äöü
[download]

You can switch the current locale in your perl program reading locale or perllocale.

And BTW: lc is the same as "\L".

-- Frank