Yet Another Way to capture first matching file, if any, and number of matching files concisely:

c:\@Work\Perl\monks>perl -wMstrict -le
"my @files = qw(xxx  1st_CF_xx  CF__  2nd_CF_yy  CF);
 ;;
 my $n_CF_ = my ($first_CF_) = grep /_CF_/, @files;
 ;;
 print qq{number of _CF_ files: $n_CF_};
 if ($n_CF_ == 1) { print qq{just one: '$first_CF_'}; }
"
number of _CF_ files: 2

c:\@Work\Perl\monks>perl -wMstrict -le
"my @files = qw(xxx  1st_CF_xx  CF__  CF);
 ;;
 my $n_CF_ = my ($first_CF_) = grep /_CF_/, @files;
 ;;
 print qq{number of _CF_ files: $n_CF_};
 if ($n_CF_ == 1) { print qq{just one: '$first_CF_'}; }
"
number of _CF_ files: 1
just one: '1st_CF_xx'

c:\@Work\Perl\monks>perl -wMstrict -le
"my @files = qw(xxx  yyy  zzz);
 ;;
 my $n_CF_ = my ($first_CF_) = grep /_CF_/, @files;
 ;;
 print qq{number of _CF_ files: $n_CF_};
 if ($n_CF_ == 1) { print qq{just one: '$first_CF_'}; }
"
number of _CF_ files: 0
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Update: Be aware that if no files match the grep condition in the example code above,  $first_CF_ is undefined.