Use of uninitialized value $v in concatenation (.) or string at mytest.pl line 12, <DATA> line 1.
The [main] key has  value

The foo key has bar value

The baz key has buzz value

Use of uninitialized value $k in concatenation (.) or string at mytest.pl line 12, <DATA> line 4.
Use of uninitialized value $v in concatenation (.) or string at mytest.pl line 12, <DATA> line 4.
The  key has  value

Use of uninitialized value $v in concatenation (.) or string at mytest.pl line 12, <DATA> line 5.
The [config] key has  value

The bingo key has 42 value