Or simpler

my @files = io('.')->all_files;
$files[0] > io( "/tmp/$files[0]" );
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By forcibly stringifying your original solution should work as well:

my @files = io('.')->all_files;
io( "$files[0]" ) > io( "/tmp/$files[0]" );
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But I don't want to be the maintenance programmer then..

But, are you using @files at all otherwise? Sounds like you just want the first — in which case I'd use

my $file = io( '.' )->next;
$file > io( "/tmp/$file" );
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Also, are you sure you need the file named after the original? If not, it's better to let IO::All pick a temporary name for you.

my $tmp = io;
io( '.' )->next > $tmp;
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