I'd consider it Perlish, because it gets the job done and is quite legible. However, you could do it on one line with a map if that feels Perlier to you:

my %csvColumns = map {$csvColumns[$_] => $_} 0 .. $#csvColumns;
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Or you could use an explicit iterator with a do to limit scope:

my %csvColumns = do {my $i = 0; map {$_ => $i++} @csvColumns};
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I know lots of folks would describe those as Perlier, though would not be using the phrase in a positive way.