#! /usr/bin/perl
use strict;
use warnings;
use Tie::File;

my $file = 'data.txt';

tie my @file, 'Tie::File', $file   or die "tie '$file' failed.\n";

while ( defined $file[-1] && $file[-1] !~ m/\{$/ ) {
    pop @file;
}

untie @file;