my @match;
while (<>)) {
   my @caps = /pat/
      or next;
   @match = @caps;
}

if (@match) {
    print("Captured @match\n");
} else {
    die("No match\n");
}
[download]

my $match;
while (<>)) {
   $match = $_ if /pat/;
}

if (defined($match)) {
    print("Matched $match");
} else {
    die("No match\n");
}
[download]

All this guessing is leading to suboptimal solutions and wated work. If this is still not good, please provide more info about your problem.

No... its not on a single variable... i am opening the file and reading it line by line...

Try:

my $last_line = undef;
while( <$fh> ){
  $last_line = $_;
  # process file contents, if needed
}
if( defined $last_line ){
  $last_line =~ m/$pat\z/;
}else{
  warn "file is empty\n";
}

That will erroneously claim the file is empty if the last occurrence of the pattern in on the second-last line (for example).