Re^2: Perl oddities (s/// doesn't DWIM in map)

[Roy Johnson]

A related oddity is that map can modify its input, in addition to generating output. That leads to the pitfall of

my @new = map { s/foo/bar/; $_ } @old;
# @old is modified along with @new!
# should be my @new = map { s/foo/bar/; $_ } map {$_} @old;

If map couldn't modify its input, the whole "map in a void context" debate might never have happened. for would be used for modifying input, map would be used for generating new output. Of course, it's a tradeoff, giving up some liberty for safety.