open(IN, "/some/file") || die "Cant open /some/file: $!\n";
while (<IN>) {
   next unless (m/^$some_match/);
   chomp($capture = $_);
}
close(IN);

##</code><code>##

open(IN, "/some/file") || die "Cant open /some/file: $!\n";
chomp( ($capture) = grep(/^$some_match/, <IN>) );
close(IN);