As a Fool, I love it when the stock price of a perfectly solid company takes an irrational tumble. I think that's exactly what happened to office-supply retailer Staples (NASDAQ:SPLS) after it announced first-quarter earnings yesterday.

Earnings, sales, and comps were all higher in the quarter. Heck, even free cash flow was way up, and the company repurchased 7.2 million shares of its stock in the quarter. So, yeah, I'm seeing all kinds of reasons why the stock price finished more than 2% lower, and was down more than 5% at times, after news like that.

Perhaps a closer look at the results will shed some light on the sudden sell-off at Staples. In the first quarter, earnings improved 12.4% to $209 million, and sales were 8.3% higher to $4.6 billion. The retailer improved free cash flow by 139%, so I'm guessing that's not the problem. Investors' concern lies instead with the company's sluggish U.S. sales, up just 3%, with comps edging up 1%. Although international sales rose 16%, in local currency the gain was a more modest 5%.

Concerns about a relatively weak U.S. sales environment led management to approach the remainder of the year cautiously. Although it didn't touch its full-year earnings forecast of $1.43 to $1.49 per share, it expects to finish near the lower end of that guidance. However, it still expects earnings to grow by 15% to 20%, combined with double-digit sales growth.

I realize that Staples is in a fierce battle with fellow office suppliers Office Depot (NYSE:ODP) and OfficeMax (NYSE:OMX) as well as big-box retailers like Wal-Mart (NYSE:WMT), but Staples remains the market leader. Concerns about a slowdown in the U.S. market are certainly justified, but when a company is predicting Staples' level of growth, it's hardly struggling to remain afloat.

Staples continues to be a solid performer with good management. It maintains a mountainous stockpile of cash, and it's growing well internationally. Investors waiting for a sale at Staples may have just gotten the dip they've been waiting for.

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Fool contributor Mike Cianciolo owns shares of Wal-Mart, but holds no financial position in other company in this article. The Fool's disclosure policy believes you have its stapler.