{ starts both hash references and blocks, so map { ... could be either the start of map BLOCK LIST or map EXPR, LIST. Because Perl doesn't look ahead for the closing } it has to take a guess at which it's dealing with based on what it finds just after the {. Usually it gets it right, but if it doesn't it won't realize something is wrong until it gets to the } and encounters the missing (or unexpected) comma. The syntax error will be reported close to the }, but you'll need to change something near the { such as using a unary + or semicolon to give Perl some help:

use warnings;
use strict;

@_ = 'a' .. 'c';

print @_[
map +($_ -1),
grep { $_ > 0 and $_ <= 1 }
map { $_ + 1 } -1..1
];
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