So, I might be mistaken here, but:

sub { my @e = map { $_ if (s/0/./g || 1) } @elem }

modifies global @elem in place. The s///g acts on $_, which is an alias to the list item. After the first iteration of mapc, you've altered the sample data. Not sure that matters, as this is a /g it has to inspect all the characters regardless.

As has been mentioned already, the map versions both have two needless logical branches, which taints the results.

A better comparison might be something that doesn't act in-place. Like an addition: 

my @b = map { $_ + 2 } @elem;
# vs
my @b;
for ( @elem ) { push @b, $_ + 2; }

# -> results:
#             Rate       map       for
# map       60.3/s        --      -23%
# for       78.2/s       30%        --

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In reply to Re: When should I use map, for? by fishbot_v2
in thread When should I use map, for? by radiantmatrix

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