for (...) {
   push @a, $_;
}

##</code><code>##

push @a, ...;

##</code><code>##

my @a = ...;

##</code><code>##

unless ( ($localtimenoformat - $mdtmnoformat) > 3600 ) {

##</code><code>##

if ( ($localtimenoformat - $mdtmnoformat) <= 3600 ) {

##</code><code>##

     push @files, $ftp->ls;

     my $new_file = 0;
     my $current_time_epoch = time;
     for my $file (@files) {
        my $modified_time_epoch = $ftp->mdtm($file);
        if ( ($current_time_epoch - $modified_time_epoch) <= 3600 ) {
           print "$file\n";
           print "Current time =  $current_time_epoch\n";
           print "MDTM         =  $modified_time_epoch\n";
           $new_file = 1;
        }
     }

     envia_mail() if !$new_file;
     $ftp->quit or die $ftp->message;

##</code><code>##

     push @files, $ftp->ls;

     my $new_file = 0;
     my $current_time_epoch = time;
     for my $file (@files) {
        if ( ($current_time_epoch - $ftp->mdtm($file) ) <= 3600 ) {
           $new_file = 1;
           last;
        }
     }

     envia_mail() if !$new_file;
     $ftp->quit or die $ftp->message;