grep -F -f file1 file2 file3 file4 file5

##</code><code>##

my %matches = map {/(.*)/, 1}, do {local @ARGV = "file1"; <>};
local @ARGV = ("file2", "file3", "file4", "file5");
while (<>) {
    /^(\S+)/ && $matches{$1} && print
}