"virtually perfect" is correct and can be used in written English.
"Virtually perfect" is appropriate when you want to talk about something that is almost, but not quite perfect. For example: "The newly renovated hotel looks virtually perfect."
And the oxygen level was 98%, virtually perfect.
But that virtually perfect putting stroke wasn't an accident.
He cited the "virtually perfect fit between your needs and my skills".
Miller's film showed dramatically the virtually perfect preservation of Clive's musical powers and memory.
In short, given the nature of the crisis, Burke extended the virtually perfect public apology.
Harvard played a virtually perfect first half in taking a 27-0 lead.
Both broadcasters will be delighted since the Europa League is virtually perfect at present.
The superb albums Mr. N'Dour has released to the world market since the early 1990's -- among them "Set" in 1992, "Joko (the Link)" in 2000 and "Nothing's in Vain" in 2002 -- all approached a gleaming, high-tech African-world-pop fusion that Mr. N'Dour virtually perfected.
Shareability is a new type of media company, one that has virtually perfected the process of delivering blockbuster (read: viral) brand videos.
Though stream of consciousness has become passé in the minds of many contemporary writers and critics, the style was still prepubescent when Joyce virtually perfected it in Ulysses -- published three years before Virginia Woolf's Mrs Dalloway, and a full eight years before Faulkner's As I Lay Dying, both considered preeminent texts of the style.
In addition, the associated 95%% confidence intervals virtually matched the almost perfect range of kappa values.
