#!/usr/bin/perl
use strict;
use warnings;
my $outs = <<'EOS';
A B C
A B D
A D E
EOS
print $outs;
my %hash;
foreach (split ' ',$outs)
{
$hash{$_}++;
}
print "Values occurring exactly twice:\n";
foreach (keys %hash)
{
print "$_\n" if ($hash{$_} ==2);
}
__END__
A B C
A B D
A D E
Values occurring exactly twice:
B
D
####
#!/usr/bin/perl
use strict;
use warnings;
my $outs = <<'EOS';
A B C
A B D
A D E
EOS
if ( (()=$outs =~ m|D|g)==2) { print "exactly 2 matches for D\n" }
# I think better written as:
my @matches = $outs =~ m|D|g;
print "exactly 2 matches for D\n" if @matches ==2;
##
##
if ( $outs =~ tr/D// == 2) { print "exactly 2 matches for D\n" }