Exit the Foreach Loop after fetching once value in XSL Template

Summary

We have an requirement where if there are multiple Invoice lines with PO numbers,but we have to fetch any one of the PO number from lines in XSL template from Payment xml.

Content

In payment xml, we have "DocumentPayableLine" tag which refers the Invoice line and has line details.
In this xml we have four  DocumentPayableLine tags.
Two of them have PONumber Populated and other two have Null for PONumber.
I am using a "foreach" loop to iterate through the DocumentPayableLine and "if" statement to check if PO number is not null.
I am able to fetch two values for PONumber as two DocumentPayableLine has PONumbers populated, but I want to print only one PONumber.