Problems and suggestions:

• Simplify your grep by using the /i flag to make it case-insensitive.
• Since the foreach loop puts each filename in $_, $ucount is completely superfluous and likely to confuse things.
• You put a matched filename in $frameu and then....do nothing with it.
• You print the filenames that don't match.
• You increment the counter, but can you be certain the counter will always correspond to the number in the filename?
• I think what you want is to find the largest-numbered file in the directory, and then print the next-largest number.

So, rewriting with those things in mind:

#!/usr/bin/perl
use strict;
use warnings;

my $topdir = 'D:/PGN/ELSEVIER/FNS/1(1)/press';
opendir HU, $topdir; # don't quote a single scalar
my @files = grep /\.txt$/i, readdir HU;   # will also match .TXT
closedir HU;

my $biggest = 0;  #keep track of largest number found
for my $frame (@files){
    if($frame =~ m|^partial_pressps_report(\d+)|){
        my $n = $1;            # capture number from filename
        if( $n > $biggest ){   # is it bigger than $biggest?
            $biggest = $n;     # then save it
        }
    }
}
$biggest++;      # got the largest one, now increment it
print $biggest;  # and print it
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Hi Monk

the last file name have to be incremented from the list pls refer the increment the last file name thread

Thanks, Ahmed