It's not working because s/// returns the number of replacements that it did, not the string after replacement. If you want that, you can say map { s/.../.../; $_ } @stuff. Note, however, that this modifies the original list. Since you're modifying the values in place anyway, you might as well use a for loop instead. 

s/(.*)/    $1\n/ for @small_files;

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The error you get without the parentheses on grep is (at least when I tried it): 

Warning: Use of "-s" without parentheses is ambiguous
Unterminated <> operator

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You can disambiguate -s by putting $_ in the expression explicitly. 

my @small_files = grep -s $_ < 10_000, @ARGV;

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Otherwise, it thinks that you were going to say something like -s <STDIN> but forgot the closing >.

In reply to Re: Newbie: parentheses, map, etc. by kyle
in thread Newbie: parentheses, map, etc. by nefigah

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