DB<100> map {+2,$_} 1..3   # +2 is not a hash key
 => (2, 1, 2, 2, 2, 3)

 DB<101> map {2,$_} 1..3    # 2 is a hash key 
           ;;
Not enough arguments for map at (eval 21)[multi_perl5db.pl:644] line
2, near "} 1"
syntax error at (eval 21)[multi_perl5db.pl:644] line 2, near "} 1"

  DB<102> map {2,$_}, 1..3  # 2 is a hash key
 => ({ 2 => 1 }, { 2 => 2 }, { 2 => 3 })

  DB<103> map {+2,$_}, 1..3 # +2 is not a hash key
           ;;
syntax error at (eval 26)[multi_perl5db.pl:644] line 2, near "},"

  DB<104> map {+2 => $_}, 1..3 # +2 is not a hash key even with fat comma
           ;;
syntax error at (eval 29)[multi_perl5db.pl:644] line 2, near "},"

##</code><code>##

  DB<105> map +{+2 => $_}, 1..3 # +2 IS A HASH KEY
 => ({ 2 => 1 }, { 2 => 2 }, { 2 => 3 })

  DB<106> map +{+2 , $_}, 1..3  # +2 IS A HASH KEY even without =>
 => ({ 2 => 1 }, { 2 => 2 }, { 2 => 3 })