I have 2 dataframes: df1 and df2. I would like to merge the 2 dataframes on the column link in df2. Link column in df2 contains a list of column and values which match in df1:

```
df1 = pd.DataFrame({'p':[1,2,3,4], 'a':[1,2,2,2],'b':['z','z','z','z'],'c':[3,3,4,4],'d':[5,5,5,6]})

df2 = pd.DataFrame({'e':[11,22,33,44], 'link':['a=1,c=3','a=2,c=3','a=2,c=4,d=5','a=2,c=4']})

```

The result should end with dataframe like this where column e from df2 are merge together with df1:

```
df_res = pd.DataFrame({'p':[1,2,3,3,4], 'a':[1,2,2,2,2],'b':['z','z','z','z','z'],'c':[3,3,4,4,4],'d':[5,5,5,5,6],'e':[11,22,33,44,44]})

```

How can this be done in pandas?