You can run external commands in Perl with system(), exec() or backticks/qx():-

# Note escaped slashes!
system("xcopy dos.bat \\\\machine.b\\share\\")
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You might also find the Shell module useful, as it will allow you to use xcopy as if it were a Perl command:-

use Shell qw(xcopy);
xcopy("dos.bat", "\\\\machine.b\\share\\");
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However, Perl does support UNC-style paths (if your OS does), so you could use plain ol' open() or a more elaborate (robust?) wrapper like File::Copy:-

open LOCAL, "dos.bat" or die $!;
open REMOTE, "//machine.b/share/dos.bat" or die $!;
print REMOTE <LOCAL>;

use File::Copy;
copy("dos.bat", "//machine.b/share/dos.bat") or die $!;
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(Note that the native Perl calls support the alternate use of forwardslashes, which will save you from excessive escaping of UNC paths.)