sub apply_filter {
    my $subref = shift;
    return map { &$subref($_) } @_ if (wantarray);  # Copy for arrays
    return &$subref($_[0]) if (defined(wantarray)); # Copy for scalar
    $_ = &$subref($_) foreach (@_);                 # In-place
    return;
}

sub detaint {
    return apply_filter(sub { $_[0] =~ /^(.*)$/; $1 }, @_);
}

# Refactored code leads to reuse!
sub left_pad {
    my $padding = shift;
    my $minlength = length($minlength);
    return apply_filter(sub {
        my $v = shift;
        if (length($v) < $minlength) {
            ($padding . $v) =~ /(.{$minlength})$/;
            $v = $1;
        }
        $v;
    }, @_);
}