while (<FICC>) {
  my @words = split /\s+/,lc $_;
  ++$uniq1{$_} for @words;
}

[download]

$uniq1{$_} contains all the words from file1 like a dictionary. $uniq1{'anyword'} will be undef or 0 if 'anyword' was not in file1.
Try a simple example

#!perl
my %uniq1= (
  cow => 1,
  dog => 1,
  fox => 1,
);

my @words = ('ant','bat','cat','dog','eel','fox');
my @match = grep $uniq1{$_}, @words;
print "@match\n"

[download]
poj

In reply to Re^13: compare two text file line by line, how to optimise by poj
in thread compare two text file line by line, how to optimise by thespirit

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