my $fractionString = "1/2";
my $fractionValue = ( $fractionString =~ m{^(\d+)/([1-9]\d*)} ) ? $1/$2 : "undefined";
print "$fractionString is actually $fractionValue <br>";

##</code><code>##

$fractionString =~ s{(\d+)/([1-9]\d*)}{$1/$2}e;