$s = '1START   ACCOUNTA     XXXXXMA      12345     XYZ111          1START ...';;
print $1 while $s =~ m[((?:\S+\s+){5})]g;;
1START   ACCOUNTA     XXXXXMA      12345     XYZ111
1START   ACCOUNTB     XXXXXBR      12345     XYZ191
1START   ACCOUNTA     XXXXXNY      54321     XYZ131