You can parse it into numerator/denomenator: 
  my $s = "6/2";
  my($num,$de)= split /\//,$s;

[download]
or just eval: 
  my $s = "6/2";
  4 + eval($s); # 7

[download]

In reply to Re: Arithmetic with fractions by johnnywang
in thread Arithmetic with fractions by algonquin

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