$ perl  -le " print for grep { my $what = scalar($Q++==0 ..($_ eq q{Q})); warn $what; $what } qw{ a b c Q r s }; "
1 at -e line 1.
2 at -e line 1.
3 at -e line 1.
4E0 at -e line 1.
Warning: something's wrong at -e line 1.
Warning: something's wrong at -e line 1.
a
b
c
Q