after substituting given word with respected value i want to do math operation. like i open 1 file in starting of the file i m having all d word with respected value wich store it in hash and i replace it also now i want to do some mathematical operzation on the same line wheere substitution happen like

 hi=3 ; 
my=4; 
#before substitution. 
hi + my 
# after substitution  
3 +4. 
now i want  
7
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