local *FILE2;
open(FILE2, '<', 'file2')
or die(...);

my %file2 = map { /^(\S+)/; ($1 => $_) } <FILE2>;

close(FILE2);


local *FILE1;
open(FILE1, '<', 'file1')
or die(...);

while (<FILE1>) {
   chomp;
   print($file2{$_}) if (exists($file2{$_}));
}

close(FILE1);
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