The hash does seem to have something to do with it. Strawberry Perl 5.20.0:

C:\Users\>perl -e "use List::Util qw(first); my $f = first { lc $_ eq 
+'qwe' } qw(QWE); print $f"
QWE
C:\Users\>perl -e "use List::Util qw(first); %h = qw(QWE 1); my $f = f
+irst { lc $_ eq 'qwe' } keys %h; print $f"
qwe
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