As the number of columns provided in ls -l are constant, how about splitting out each element of the column in to a variable and then matching the first four characters of the filename?

@namearr = `ls -l`;
foreach $nameline (@namearr)
{
   chomp $nameline;
   print ("'$nameline'\n");
   ($var1, $var2, $var3, $var4, $var5, $var6, $var7, $var8, $name) = (
+split " ", $nameline);
   $name =~ s/^(\w{4}).+/$1/;
   print ("NAME '$name'\n");
}
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The regex part matches the first four characters and substitutes the match in to the $name variable