Thanks to Eliya, muba and ww. It turned out the Perl solution was not a Perl solution. I discovered by accident that the unwanted newlines could be removed by saving the Visio .vsx (stencil) file to a Visio.vdx (drawing) file. (Simply removeing all newlines was no good because it created one long 70-Mb line.) Since you are a religious order, you will be want to know what moral lesson I drew from this. It is that the tool you used to create the file on which you are going to run Perl often has the means to make the file more presentable to Perl, which is to say more worthy of Perl.