I have a 100MB plain text database file which I would like to parse and convert into datastructure for easy access. The environment is perl and cygwin. Since we receive the plain text file with data from third party, I am not able to use any existing parser like xml or google protocol buffers. 

Text file looks like below.

```
Class=Instance1
parameterA = <val>
parameterB = <val>
parameterC = <val>
ref = Instance2

Class=Instance2
parameterA = <val>
parameterB = <val>
parameterC = <val>

```

The file contains a huge number class variants.

What would be the best option to parse this ? Will yacc/lex help me or should i write my own perl parser ?