map { push( @{$_ % 2 ? \@odd : \@even }, "+$_" ) } @numbers;
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On my (perl 5.24) system, your original code says:

Experimental push on scalar is now forbidden at pf.pl line 13, near ""
++$_" ) "
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Update: BTW - "map" is not the best choice for this code, because you are throwing away the result of the map.

Preferred, and more concise:

 push( @{$_ % 2 ? \@odd : \@even }, "+$_" ) for @numbers;
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Then there is room for optimization:

my @evenodd = (\@even, \@odd);
push( @{$evenodd[$_ % 2]}, "+$_" ) for @numbers;
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